package control

import (
	"errors"
	"fmt"
	"io"
	"slices"
	"strconv"
	"strings"
	"time"

	"gitbay.org/gitbay/internal/gitutil"
	"gitbay.org/gitbay/internal/policy"
	"gitbay.org/gitbay/internal/protocol"
	"gitbay.org/gitbay/internal/sig"
	"gitbay.org/gitbay/internal/store"
)

func init() {
	register(Command{Path: []string{"repo", "fork"},
		Summary: "fork a repository under your account",
		Usage:   "repo fork <owner/name> [--name <n>]", Run: runRepoFork})
	register(Command{Path: []string{"repo", "settings", "require-approvals"},
		Summary: "require N fresh approvals to merge",
		Usage:   "repo settings require-approvals <owner/name> <n> (0 = off)", Run: runRequireApprovals})
	register(Command{Path: []string{"repo", "settings", "require-resolved"},
		Summary: "require all review threads resolved to merge",
		Usage:   "repo settings require-resolved <owner/name> on|off", Run: runRequireResolved})
	register(Command{Path: []string{"repo", "settings", "require-codeowners"},
		Summary: "require an owner's approval for every file CODEOWNERS covers",
		Usage:   "repo settings require-codeowners <owner/name> on|off", Run: runRequireCodeowners})
	register(Command{Path: []string{"repo", "settings", "require-checks"},
		Summary: "gate merges on green statuses",
		Usage:   "repo settings require-checks <owner/name> on|off", Run: runRequireChecks})
	register(Command{Path: []string{"repo", "settings", "require-signed"},
		Summary: "require verified commit signatures",
		Usage:   "repo settings require-signed <owner/name> on|off", Run: runRequireSigned})
	register(Command{Path: []string{"mr", "create"},
		Summary:    "open a merge request",
		Usage:      "mr create <target owner/name> --source [owner/name:]<branch> --target <branch> --title <t> [--body <b> | --file -] [--format md|org] [--draft]",
		ReadsStdin: true, Run: runMRCreate})
	register(Command{Path: []string{"mr", "range-diff"},
		Summary:  "what changed between two revisions of a merge request",
		Usage:    "mr range-diff <owner/name> <n> [--from <sha>] [--to <sha>]",
		ReadOnly: true, Run: runMRRangeDiff})
	register(Command{Path: []string{"mr", "revisions"},
		Summary:  "the heads a merge request has had",
		Usage:    "mr revisions <owner/name> <n>",
		ReadOnly: true, Run: runMRRevisions})
	register(Command{Path: []string{"mr", "draft"},
		Summary: "mark a merge request as work in progress",
		Usage:   "mr draft <owner/name> <n>", Run: runMRDraft})
	register(Command{Path: []string{"mr", "ready"},
		Summary: "take the draft mark off, so it can merge",
		Usage:   "mr ready <owner/name> <n>", Run: runMRReady})
	register(Command{Path: []string{"mr", "list"},
		Summary: "list merge requests",
		Usage:   "mr list <owner/name> [--state open|merged|closed|source_gone|all] [--author <user>] [--milestone <title>|none] [--search <text>] [--limit <n>] [--cursor <c>]", ReadOnly: true, Run: runMRList})
	register(Command{Path: []string{"mr", "show"},
		Summary: "show a merge request",
		Usage:   "mr show <owner/name> <n>", ReadOnly: true, Run: runMRShow})
	register(Command{Path: []string{"mr", "diff"},
		Summary: "show the diff",
		Usage:   "mr diff <owner/name> <n>", ReadOnly: true, Run: runMRDiff})
	register(Command{Path: []string{"mr", "edit"},
		Summary:    "edit title or body",
		Usage:      "mr edit <owner/name> <n> [--title <t>] [--body <b> | --file -] [--format md|org]",
		ReadsStdin: true, Run: runMREdit})
	register(Command{Path: []string{"mr", "retarget"},
		Summary: "retarget onto another branch",
		Usage:   "mr retarget <owner/name> <n> <branch>", Run: runMRRetarget})
	register(Command{Path: []string{"mr", "comment"},
		Summary:    "comment",
		Usage:      "mr comment <owner/name> <n> [--message <m> | --file -] [--format md|org]",
		ReadsStdin: true, Run: runMRComment})
	register(Command{Path: []string{"mr", "review"},
		Summary: "review",
		Usage:   "mr review <owner/name> <n> --approve|--request-changes|--comment|--discard", Run: runMRReview})
	register(Command{Path: []string{"mr", "merge"},
		Summary: "merge",
		Usage:   "mr merge <owner/name> <n> [--strategy ff|merge|squash|rebase]", Run: runMRMerge})
	register(Command{Path: []string{"mr", "close"},
		Summary: "close without merging",
		Usage:   "mr close <owner/name> <n>", Run: runMRClose})
}

func runRepoFork(c *Ctx, args []string) int {
	f, err := parseFlags(args, flagSpec{Values: []string{"--name"}, MaxPos: 1, Usage: "repo fork <owner/name> [--name <n>]"})
	if err != nil {
		return c.fail(protocol.ExitUsage, "%v", err)
	}
	path, name := f.pos(0), f.Value("--name")
	if path == "" {
		return c.fail(protocol.ExitUsage, "usage: repo fork <owner/name> [--name <n>]")
	}
	src, code := resolveRepo(c, path, policy.CanRead)
	if code >= 0 {
		return code
	}
	if name == "" {
		name = src.Name
	}
	if err := policy.ValidateName(name); err != nil {
		return c.failErr(err)
	}
	repoCreateMu.Lock()
	if code := checkRepoQuota(c); code >= 0 {
		repoCreateMu.Unlock()
		return code
	}
	id, err := c.Store.CreateFork("user", c.User.ID, name, src.Visibility, src.ID)
	repoCreateMu.Unlock()
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	dstDir := RepoDir(c.Cfg.Server.Root, c.User.Username, name)
	srcDir := RepoDir(c.Cfg.Server.Root, src.OwnerName, src.Name)
	if err := gitutil.InitBare(dstDir, "main", HooksDir(c.Cfg.Server.Root)); err != nil {
		c.Store.DeleteRepo(id)
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	if desc := gitutil.ReadDescription(srcDir); desc != "" {
		gitutil.WriteDescription(dstDir, desc)
	}
	if err := gitutil.FetchInto(dstDir, srcDir, "refs/heads/*", "refs/heads/*"); err != nil {
		// Empty source repos have nothing to fetch; that is fine.
		if _, rerr := gitutil.ResolveRef(srcDir, src.DefaultBranch); rerr == nil {
			c.Store.DeleteRepo(id)
			return c.fail(protocol.ExitFailure, "copying refs: %v", err)
		}
	}
	forkPath := c.User.Username + "/" + name
	return c.emit(map[string]string{"path": forkPath, "fork_of": src.Path()}, func(w io.Writer) {
		fmt.Fprintf(w, "forked %s to %s\n", src.Path(), forkPath)
	})
}

func runRequireApprovals(c *Ctx, args []string) int {
	if len(args) != 2 {
		return c.fail(protocol.ExitUsage, "usage: repo settings require-approvals <owner/name> <n>")
	}
	n, err := strconv.Atoi(args[1])
	if err != nil || n < 0 || n > 20 {
		return c.fail(protocol.ExitUsage, "approvals must be 0..20")
	}
	repo, code := resolveRepo(c, args[0], policy.CanAdmin)
	if code >= 0 {
		return code
	}
	s, err := c.Store.UpdateRepoSettings(repo.ID, func(s *store.RepoSettings) { s.RequireApprovals = n })
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	return c.emit(s, func(w io.Writer) {
		fmt.Fprintf(w, "require_approvals %d on %s\n", n, repo.Path())
	})
}

func runRequireResolved(c *Ctx, args []string) int {
	if len(args) != 2 || (args[1] != "on" && args[1] != "off") {
		return c.fail(protocol.ExitUsage, "usage: repo settings require-resolved <owner/name> on|off")
	}
	repo, code := resolveRepo(c, args[0], policy.CanAdmin)
	if code >= 0 {
		return code
	}
	s, err := c.Store.UpdateRepoSettings(repo.ID, func(s *store.RepoSettings) { s.RequireResolved = args[1] == "on" })
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	return c.emit(s, func(w io.Writer) {
		fmt.Fprintf(w, "require_resolved %s on %s\n", args[1], repo.Path())
	})
}

func runRequireCodeowners(c *Ctx, args []string) int {
	if len(args) != 2 || (args[1] != "on" && args[1] != "off") {
		return c.fail(protocol.ExitUsage, "usage: repo settings require-codeowners <owner/name> on|off")
	}
	repo, code := resolveRepo(c, args[0], policy.CanAdmin)
	if code >= 0 {
		return code
	}
	s, err := c.Store.UpdateRepoSettings(repo.ID, func(s *store.RepoSettings) { s.RequireCodeowners = args[1] == "on" })
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	return c.emit(s, func(w io.Writer) {
		fmt.Fprintf(w, "require_codeowners %s on %s\n", args[1], repo.Path())
	})
}

func runRequireChecks(c *Ctx, args []string) int {
	if len(args) != 2 || (args[1] != "on" && args[1] != "off") {
		return c.fail(protocol.ExitUsage, "usage: repo settings require-checks <owner/name> on|off")
	}
	repo, code := resolveRepo(c, args[0], policy.CanAdmin)
	if code >= 0 {
		return code
	}
	s, err := c.Store.UpdateRepoSettings(repo.ID, func(s *store.RepoSettings) { s.RequireChecks = args[1] == "on" })
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	return c.emit(s, func(w io.Writer) {
		fmt.Fprintf(w, "require_checks %s on %s\n", args[1], repo.Path())
	})
}

func runRequireSigned(c *Ctx, args []string) int {
	if len(args) != 2 || (args[1] != "on" && args[1] != "off") {
		return c.fail(protocol.ExitUsage, "usage: repo settings require-signed <owner/name> on|off")
	}
	repo, code := resolveRepo(c, args[0], policy.CanAdmin)
	if code >= 0 {
		return code
	}
	s, err := c.Store.UpdateRepoSettings(repo.ID, func(s *store.RepoSettings) { s.RequireSignedCommits = args[1] == "on" })
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	return c.emit(s, func(w io.Writer) {
		fmt.Fprintf(w, "require_signed_commits %s on %s\n", args[1], repo.Path())
	})
}

// mrRef parses "<owner/name> <n>" and loads the MR.
func mrRef(c *Ctx, args []string, perm func(store.User, store.Repo, string) bool) (store.Repo, store.MR, int) {
	repo, n, code := refArgs(c, args, perm, "MR")
	if code >= 0 {
		return repo, store.MR{}, code
	}
	mr, err := c.Store.MRByNumber(repo.ID, n)
	if errors.Is(err, store.ErrNotFound) {
		return repo, mr, c.fail(protocol.ExitNotFound, "MR !%d not found in %s", n, repo.Path())
	}
	if err != nil {
		return repo, mr, c.fail(protocol.ExitFailure, "%v", err)
	}
	return repo, mr, -1
}

func mrHeadRef(n int64) string { return fmt.Sprintf("refs/merge-requests/%d/head", n) }

func runMRCreate(c *Ctx, args []string) int {
	f, err := parseFlags(args, flagSpec{Values: []string{"--source", "--target", "--title", "--body", "--file", "--format"},
		Bools: []string{"--draft"}, MaxPos: 1,
		Usage: "mr create <target owner/name> --source [owner/name:]<branch> --target <branch> --title <t> [--draft]"})
	if err != nil {
		return c.fail(protocol.ExitUsage, "%v", err)
	}
	path, source, target := f.pos(0), f.Value("--source"), f.Value("--target")
	title, body, file, format := f.Value("--title"), f.Value("--body"), f.Value("--file"), f.Value("--format")
	if path == "" || source == "" || title == "" {
		return c.fail(protocol.ExitUsage, "usage: mr create <target owner/name> --source [owner/name:]<branch> --target <branch> --title <t> [--draft]")
	}
	fmtName, err := markupFormat(format)
	if err != nil {
		return c.failErr(err)
	}
	if fmtName == "" {
		fmtName = "md"
	}
	repo, code := resolveRepo(c, path, policy.CanRead)
	if code >= 0 {
		return code
	}
	if code := refuseArchived(c, repo); code >= 0 {
		return code
	}
	if target == "" {
		target = repo.DefaultBranch
	}

	// Source is "branch" (same repo) or "owner/name:branch" (a fork).
	srcRepo := repo
	srcBranch := source
	if sp, br, ok := strings.Cut(source, ":"); ok {
		srcBranch = br
		var scode int
		srcRepo, scode = resolveRepo(c, sp, policy.CanRead)
		if scode >= 0 {
			return scode
		}
		if srcRepo.ForkOf != repo.ID && srcRepo.ID != repo.ID {
			return c.fail(protocol.ExitUsage, "%s is not a fork of %s", srcRepo.Path(), repo.Path())
		}
	}
	srcDir := RepoDir(c.Cfg.Server.Root, srcRepo.OwnerName, srcRepo.Name)
	headSHA, err := gitutil.ResolveRef(srcDir, "refs/heads/"+srcBranch)
	if err != nil {
		return c.fail(protocol.ExitNotFound, "branch %s not found in %s", srcBranch, srcRepo.Path())
	}
	b, err := bodyFrom(c, body, file)
	if err != nil {
		return c.failErr(err)
	}
	n, err := c.Store.CreateMR(repo.ID, c.User.ID, srcRepo.ID, srcBranch, target, title, b, headSHA, fmtName, f.Has("--draft"))
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	// Fetch the head into the target so the target owns the objects.
	dstDir := RepoDir(c.Cfg.Server.Root, repo.OwnerName, repo.Name)
	if err := gitutil.FetchInto(dstDir, srcDir, headSHA, mrHeadRef(n)); err != nil {
		return c.fail(protocol.ExitFailure, "recording MR head: %v", err)
	}
	if srcRepo.ID != repo.ID {
		QueueMRBuilds(c.Store, c.Cfg.Server.Root, c.Cfg.Server.SiteURL, repo, c.User.ID, n, headSHA)
	}
	c.Store.RecordEvent(repo.ID, c.User.ID, "mr.created", fmt.Sprintf(`{"number":%d}`, n))
	if targets, err := c.Store.RepoNotifyTargets(repo); err == nil {
		notify(c, targets, notice{repo: repo, kind: "mr",
			subject: mrSubject(repo, n, title),
			action:  fmt.Sprintf("opened merge request !%d (%s -> %s)", n, source, target),
			excerpt: b, path: fmt.Sprintf("%s/mrs/%d", repo.Path(), n)})
	}
	out := MRCreated{Number: n, HeadSHA: headSHA}
	if p, ok, err := c.Store.OpenMRBySource(repo.ID, target); err == nil && ok {
		out.StackedOn = &stackRef{p.Number, p.Title}
	}
	return c.emit(out, func(w io.Writer) {
		fmt.Fprintf(w, "created %s!%d (%s -> %s)\n", repo.Path(), n, source, target)
		if out.StackedOn != nil {
			fmt.Fprintf(w, "stacked on !%d %s\n", out.StackedOn.Number, out.StackedOn.Title)
		}
	})
}

type mrOut struct {
	Number int64  `json:"number"`
	Title  string `json:"title"`
	State  string `json:"state"`
	// Draft is an open merge request not asking to be merged yet.
	Draft      bool   `json:"draft,omitempty"`
	Author     string `json:"author"`
	Source     string `json:"source"` // owner/name:branch, or branch, "" if gone
	TargetRef  string `json:"target_ref"`
	HeadSHA    string `json:"head_sha"`
	Body       string `json:"body,omitempty"`
	BodyFormat string `json:"body_format,omitempty"`
	Milestone  string `json:"milestone,omitempty"`
	// StackedOn is the open merge request whose source branch this one
	// targets; Stacked are the open ones targeting this one's source.
	StackedOn *stackRef  `json:"stacked_on,omitempty"`
	Stacked   []stackRef `json:"stacked,omitempty"`
	CreatedAt string     `json:"created_at"`
	MergedAt  string     `json:"merged_at,omitempty"`
	MergedBy  string     `json:"merged_by,omitempty"`
	ClosedAt  string     `json:"closed_at,omitempty"`
	ClosedBy  string     `json:"closed_by,omitempty"`
}

type stackRef struct {
	Number int64  `json:"number"`
	Title  string `json:"title"`
}

// stackOf derives the stack around m: the open merge request whose source
// branch m targets, and the open ones targeting m's source. Both only
// within m's repository; a fork's branch is not a target anything can
// stack on.
func stackOf(c *Ctx, repo store.Repo, m store.MR) (*stackRef, []stackRef) {
	if m.State != "open" {
		return nil, nil
	}
	var parent *stackRef
	if p, ok, err := c.Store.OpenMRBySource(repo.ID, m.TargetRef); err == nil && ok && p.ID != m.ID {
		parent = &stackRef{p.Number, p.Title}
	}
	var children []stackRef
	if m.SourceRepoID == repo.ID {
		if kids, err := c.Store.OpenMRsByTarget(repo.ID, m.SourceRef); err == nil {
			for _, k := range kids {
				if k.ID != m.ID {
					children = append(children, stackRef{k.Number, k.Title})
				}
			}
		}
	}
	return parent, children
}

func mrToOut(repo store.Repo, m store.MR, withBody bool) mrOut {
	src := ""
	if m.SourcePath != "" {
		if m.SourceRepoID == repo.ID {
			src = m.SourceRef
		} else {
			src = m.SourcePath + ":" + m.SourceRef
		}
	}
	o := mrOut{Number: m.Number, Title: m.Title, State: m.State, Draft: m.Draft, Author: m.Author,
		Source: src, TargetRef: m.TargetRef, HeadSHA: m.HeadSHA, Milestone: m.Milestone,
		CreatedAt: m.CreatedAt, MergedAt: m.MergedAt, MergedBy: m.MergedBy,
		ClosedAt: m.ClosedAt, ClosedBy: m.ClosedBy}
	if withBody {
		o.Body = m.Body
		o.BodyFormat = m.BodyFormat
	}
	return o
}

func runMRList(c *Ctx, args []string) int {
	args, p, code := parsePageFlags(c, args, "mr", true)
	if code >= 0 {
		return code
	}
	const usage = "usage: mr list <owner/name> [--state open|merged|closed|source_gone|all] [--author <user>] [--milestone <title>|none] [--search <text>] [--limit <n>] [--cursor <c>]"
	f := store.MRFilter{State: "open"}
	fl, err := parseFlags(args, flagSpec{Values: []string{"--state", "--author", "--milestone", "--search"}, MaxPos: 1, Usage: usage})
	if err != nil {
		return c.fail(protocol.ExitUsage, "%v", err)
	}
	path := fl.pos(0)
	if fl.Has("--state") {
		f.State = fl.Value("--state")
	}
	f.Author, f.Milestone = fl.Value("--author"), fl.Value("--milestone")
	f.Search = fl.Value("--search")
	if fl.Has("--search") {
		if err := validQuery(f.Search); err != nil {
			return c.failErr(err)
		}
	}
	valid := map[string]bool{"open": true, "merged": true, "closed": true, "source_gone": true, "all": true}
	if path == "" || !valid[f.State] {
		return c.fail(protocol.ExitUsage, usage)
	}
	repo, code := resolveRepo(c, path, policy.CanRead)
	if code >= 0 {
		return code
	}
	f.Limit, f.Before = p.queryLimit(), p.keyInt()
	mrs, err := c.Store.QueryMRs(repo.ID, f)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	mrs, next := trimPage(p, mrs, "mr", func(m store.MR) string {
		return strconv.FormatInt(m.Number, 10)
	})
	var ds []mrOut
	for _, m := range mrs {
		o := mrToOut(repo, m, false)
		o.StackedOn, _ = stackOf(c, repo, m)
		ds = append(ds, o)
	}
	return c.emitPage(p, ds, next, func(w io.Writer) {
		for _, d := range ds {
			stacked := ""
			if d.StackedOn != nil {
				stacked = fmt.Sprintf("\tstacked on !%d", d.StackedOn.Number)
			}
			state := d.State
			if d.Draft {
				state = "draft"
			}
			fmt.Fprintf(w, "!%d\t%s\t%s\t%s -> %s%s\n", d.Number, state, d.Title, d.Source, d.TargetRef, stacked)
		}
	})
}

// byWhom renders " by <user>", or nothing when the actor is unknown — an
// imported merge request carries a time but no local account.
func byWhom(user string) string {
	if user == "" {
		return ""
	}
	return " by " + user
}

func runMRShow(c *Ctx, args []string) int {
	repo, mr, code := mrRef(c, args, policy.CanRead)
	if code >= 0 {
		return code
	}
	if len(args) != 2 {
		return c.fail(protocol.ExitUsage, "usage: mr show <owner/name> <n>")
	}
	comments, err := c.Store.ListMRComments(mr.ID)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	reviews, err := c.Store.ListMRReviews(mr.ID)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	statuses, combined, err := c.Store.ChecksForCommit(repo.ID, mr.HeadSHA)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	unresolved, err := c.Store.UnresolvedThreadCount(mr.ID)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	var checks []CheckOut
	for _, st := range statuses {
		out := CheckOut{Context: st.Context, State: st.State, URL: st.TargetURL, UpdatedAt: st.UpdatedAt}
		if st.Duration > 0 {
			out.Duration = st.Duration.String()
		}
		checks = append(checks, out)
	}
	var cs []commentOut
	for _, cm := range comments {
		cs = append(cs, commentOut{cm.Author, cm.Body, cm.BodyFormat, cm.CreatedAt})
	}
	var rs []ReviewOut
	counts := ReviewersWhoCount(c.Store, repo, reviews)
	for _, r := range reviews {
		rs = append(rs, ReviewOut{r.Reviewer, r.Verdict, r.Stale, counts[r.Reviewer], r.CreatedAt})
	}
	// The commits this MR carries: base..head, the diff's range.
	var commits []CommitOut
	dir := RepoDir(c.Cfg.Server.Root, repo.OwnerName, repo.Name)
	base := mr.MergedBase
	if base == "" {
		if b, err := gitutil.MergeBase(dir, "refs/heads/"+mr.TargetRef, mrHeadRef(mr.Number)); err == nil {
			base = b
		}
	}
	if base != "" {
		if shas, err := gitutil.RevListRange(dir, base, mrHeadRef(mr.Number)); err == nil {
			for _, sha := range shas {
				subject := ""
				if raw, err := gitutil.ReadCommit(dir, sha); err == nil {
					if parsed, err := sig.ParseCommit(raw); err == nil {
						subject = parsed.Subject
					}
				}
				commits = append(commits, CommitOut{sha, subject})
			}
		}
	}
	d := MRShow{mrOut: mrToOut(repo, mr, true), Checks: checks, Combined: combined,
		UnresolvedThreads: unresolved, Commits: commits, Comments: cs, Reviews: rs}
	d.StackedOn, d.Stacked = stackOf(c, repo, mr)
	return c.emit(d, func(w io.Writer) {
		state := d.State
		if d.Draft {
			state = "draft"
		}
		fmt.Fprintf(w, "!%d %s [%s] by %s\n%s -> %s @ %.10s\n", d.Number, d.Title, state, d.Author, d.Source, d.TargetRef, d.HeadSHA)
		if d.StackedOn != nil {
			fmt.Fprintf(w, "stacked on !%d %s\n", d.StackedOn.Number, d.StackedOn.Title)
		}
		for _, k := range d.Stacked {
			fmt.Fprintf(w, "stacked: !%d %s\n", k.Number, k.Title)
		}
		if d.MergedAt != "" {
			fmt.Fprintf(w, "merged %s%s\n", d.MergedAt, byWhom(d.MergedBy))
		}
		if d.ClosedAt != "" {
			fmt.Fprintf(w, "closed %s%s\n", d.ClosedAt, byWhom(d.ClosedBy))
		}
		if d.Body != "" {
			fmt.Fprintf(w, "\n%s\n", d.Body)
		}
		for _, cm := range commits {
			fmt.Fprintf(w, "commit: %.10s %s\n", cm.SHA, cm.Subject)
		}
		for _, x := range checks {
			dur := ""
			if x.Duration != "" {
				dur = " in " + x.Duration
			}
			fmt.Fprintf(w, "check: %s %s at %s%s\n", x.Context, x.State, x.UpdatedAt, dur)
		}
		if d.UnresolvedThreads > 0 {
			fmt.Fprintf(w, "unresolved threads: %d\n", d.UnresolvedThreads)
		}
		for _, r := range rs {
			stale := ""
			if r.Stale {
				stale = " (stale)"
			}
			advisory := ""
			if !r.Counts {
				advisory = " (advisory: no write access)"
			}
			fmt.Fprintf(w, "review: %s %s%s%s at %s\n", r.Reviewer, r.Verdict, stale, advisory, r.CreatedAt)
		}
		for _, cm := range cs {
			fmt.Fprintf(w, "\n--- %s at %s\n%s\n", cm.Author, cm.CreatedAt, cm.Body)
		}
	})
}

func runMRDiff(c *Ctx, args []string) int {
	repo, mr, code := mrRef(c, args, policy.CanRead)
	if code >= 0 {
		return code
	}
	dir := RepoDir(c.Cfg.Server.Root, repo.OwnerName, repo.Name)
	head := mrHeadRef(mr.Number)
	// After a merge (especially fast-forward) the live merge-base equals
	// the head and the diff would vanish; use the recorded base instead.
	base := mr.MergedBase
	if base == "" {
		b, err := gitutil.MergeBase(dir, "refs/heads/"+mr.TargetRef, head)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		base = b
	}
	patch, truncated, err := gitutil.Diff(dir, base, head, 4<<20)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	fmt.Fprint(c.Stdout, patch)
	if truncated {
		fmt.Fprintln(c.Stderr, "diff truncated at 4 MiB; fetch the branch for the rest")
	}
	return protocol.ExitOK
}

func runMREdit(c *Ctx, args []string) int {
	rest, title, body, format, code := editText(c, args, "mr")
	if code >= 0 {
		return code
	}
	repo, mr, code := mrRef(c, rest, policy.CanRead)
	if code >= 0 {
		return code
	}
	if code := refuseArchived(c, repo); code >= 0 {
		return code
	}
	if code := authorOrWrite(c, repo, mr.Author, "edit this merge request"); code >= 0 {
		return code
	}
	if err := c.Store.UpdateMRText(mr.ID, title, body, format); err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	c.Store.RecordEvent(repo.ID, c.User.ID, "mr.edited", fmt.Sprintf(`{"number":%d}`, mr.Number))
	return c.emit(map[string]any{"number": mr.Number}, func(w io.Writer) {
		fmt.Fprintf(w, "edited %s!%d\n", repo.Path(), mr.Number)
	})
}

// runMRRetarget moves an open merge request onto another branch of the
// same repository.
func runMRRetarget(c *Ctx, args []string) int {
	if len(args) != 3 {
		return c.fail(protocol.ExitUsage, "usage: mr retarget <owner/name> <n> <branch>")
	}
	repo, mr, code := mrRef(c, args[:2], policy.CanRead)
	if code >= 0 {
		return code
	}
	if code := refuseArchived(c, repo); code >= 0 {
		return code
	}
	if code := authorOrWrite(c, repo, mr.Author, "retarget this merge request"); code >= 0 {
		return code
	}
	if mr.State == "merged" || mr.State == "closed" {
		return c.fail(protocol.ExitUsage, "!%d is %s; only an open merge request can be retargeted", mr.Number, mr.State)
	}
	target := args[2]
	if target == mr.TargetRef {
		return c.fail(protocol.ExitUsage, "!%d already targets %s", mr.Number, target)
	}
	if mr.SourceRepoID == repo.ID && target == mr.SourceRef {
		return c.fail(protocol.ExitUsage, "%s is the source branch of !%d", target, mr.Number)
	}
	dir := RepoDir(c.Cfg.Server.Root, repo.OwnerName, repo.Name)
	if _, err := gitutil.ResolveRef(dir, "refs/heads/"+target); err != nil {
		return c.fail(protocol.ExitNotFound, "branch %s not found in %s", target, repo.Path())
	}
	// The diff, the commit list and the merge gates all derive their base
	// from the target on every read, so the only thing to check here is
	// that a base exists at all: without one there is nothing to show and
	// nothing to merge.
	base, err := gitutil.MergeBase(dir, "refs/heads/"+target, mrHeadRef(mr.Number))
	if err != nil || base == "" {
		return c.fail(protocol.ExitUsage, "%s shares no history with the head of !%d", target, mr.Number)
	}
	old := mr.TargetRef
	if err := c.Store.SetMRTarget(mr.ID, target); err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	c.Store.AddMRSystemComment(mr.ID, c.User.ID, fmt.Sprintf("retargeted from %s to %s", old, target))
	c.Store.RecordEvent(repo.ID, c.User.ID, "mr.retargeted",
		fmt.Sprintf(`{"number":%d,"from":%q,"to":%q}`, mr.Number, old, target))
	if parts, err := c.Store.MRParticipants(mr.ID); err == nil {
		notify(c, parts, notice{repo: repo, kind: "mr",
			subject: mrSubject(repo, mr.Number, mr.Title),
			action:  fmt.Sprintf("retargeted !%d from %s to %s", mr.Number, old, target),
			path:    fmt.Sprintf("%s/mrs/%d", repo.Path(), mr.Number)})
	}
	return c.emit(map[string]any{"number": mr.Number, "target_ref": target, "merge_base": base}, func(w io.Writer) {
		fmt.Fprintf(w, "retargeted %s!%d from %s to %s (base %.10s)\n", repo.Path(), mr.Number, old, target, base)
	})
}

func runMRComment(c *Ctx, args []string) int {
	return runComment(c, args, mrThread, "mr",
		func(rest []string) (store.Repo, int64, int64, string, int) {
			repo, mr, code := mrRef(c, rest, policy.CanRead)
			return repo, mr.ID, mr.Number, mr.Title, code
		},
		c.Store.AddMRComment, c.Store.MRParticipants)
}

func runMRReview(c *Ctx, args []string) int {
	verdict, discard := "", false
	var rest []string
	for _, a := range args {
		switch a {
		case "--approve":
			verdict = "approve"
		case "--request-changes":
			verdict = "request_changes"
		case "--comment":
			verdict = "comment"
		case "--discard":
			discard = true
		default:
			rest = append(rest, a)
		}
	}
	const usage = "mr review <owner/name> <n> --approve|--request-changes|--comment|--discard"
	if discard && verdict != "" {
		return c.fail(protocol.ExitUsage, "--discard throws the batch away; it takes no verdict")
	}
	if verdict == "" && !discard {
		return c.fail(protocol.ExitUsage, "usage: %s", usage)
	}
	repo, mr, code := mrRef(c, rest, policy.CanRead)
	if code >= 0 {
		return code
	}
	if code := refuseArchived(c, repo); code >= 0 {
		return code
	}
	if mr.State != "open" {
		return c.fail(protocol.ExitUsage, "MR !%d is %s", mr.Number, mr.State)
	}
	// Throwing the batch away is not a review, so it stops here: no
	// verdict, no event, nobody told about comments nobody ever saw.
	if discard {
		n, err := c.Store.DiscardPendingComments(mr.ID, c.User.ID)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		return c.emit(map[string]any{"number": mr.Number, "discarded": n}, func(w io.Writer) {
			fmt.Fprintf(w, "discarded %d pending comment(s) on %s!%d\n", n, repo.Path(), mr.Number)
		})
	}
	if err := c.Store.AddMRReview(mr.ID, c.User.ID, verdict, mr.HeadSHA); err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	// The batch the reviewer composed becomes visible with the verdict,
	// which is what makes it one review rather than a trickle.
	published, err := c.Store.PublishPendingComments(mr.ID, c.User.ID)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	c.Store.RecordEvent(repo.ID, c.User.ID, "mr.reviewed",
		fmt.Sprintf(`{"number":%d,"verdict":%q}`, mr.Number, verdict))
	if parts, err := c.Store.MRParticipants(mr.ID); err == nil {
		notify(c, parts, notice{repo: repo, kind: "mr",
			subject: mrSubject(repo, mr.Number, mr.Title),
			action:  reviewAction(mr.Number, verdict, published),
			path:    fmt.Sprintf("%s/mrs/%d", repo.Path(), mr.Number)})
	}
	return c.emit(map[string]any{"number": mr.Number, "verdict": verdict, "published": published}, func(w io.Writer) {
		fmt.Fprintf(w, "reviewed %s!%d: %s", repo.Path(), mr.Number, verdict)
		if published > 0 {
			fmt.Fprintf(w, " (%d comment(s))", published)
		}
		fmt.Fprintln(w)
	})
}

func runMRMerge(c *Ctx, args []string) int {
	f, err := parseFlags(args, flagSpec{Values: []string{"--strategy"}, MaxPos: -1, Usage: "mr merge <owner/name> <n> [--strategy ff|merge|squash|rebase]"})
	if err != nil {
		return c.fail(protocol.ExitUsage, "%v", err)
	}
	strategy, rest := f.Value("--strategy"), f.Pos
	valid := map[string]bool{"": true, "ff": true, "merge": true, "squash": true, "rebase": true}
	if !valid[strategy] {
		return c.fail(protocol.ExitUsage, "--strategy must be ff, merge, squash, or rebase")
	}
	repo, mr, code := mrRef(c, rest, policy.CanWrite)
	if code >= 0 {
		return code
	}
	if code := refuseArchived(c, repo); code >= 0 {
		return code
	}
	if mr.State != "open" && mr.State != "source_gone" {
		return c.fail(protocol.ExitUsage, "MR !%d is %s", mr.Number, mr.State)
	}

	dir := RepoDir(c.Cfg.Server.Root, repo.OwnerName, repo.Name)
	targetRef := "refs/heads/" + mr.TargetRef
	targetSHA, err := gitutil.ResolveRef(dir, targetRef)
	if err != nil {
		return c.fail(protocol.ExitFailure, "target branch %s: %v", mr.TargetRef, err)
	}
	headSHA, err := gitutil.ResolveRef(dir, mrHeadRef(mr.Number))
	if err != nil {
		return c.fail(protocol.ExitFailure, "MR head ref: %v", err)
	}

	// Check gate: with require_checks, the MR head must carry statuses
	// and every one of them must be green.
	if repo.Settings.RequireChecks {
		statuses, err := c.Store.ListCommitStatuses(repo.ID, headSHA)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		switch store.CombinedStatus(statuses) {
		case "success":
		case "":
			return c.fail(protocol.ExitDenied,
				"%s requires green checks and none were reported on %.10s", repo.Path(), headSHA)
		default:
			var bad []string
			for _, st := range statuses {
				if st.State != "success" {
					bad = append(bad, st.Context+"="+st.State)
				}
			}
			return c.fail(protocol.ExitDenied,
				"%s requires green checks; %.10s has %s", repo.Path(), headSHA, strings.Join(bad, ", "))
		}
	}

	// Review gates: approvals, CODEOWNERS, resolved threads.
	if code := c.reviewGates(repo, mr, dir, targetSHA, headSHA); code >= 0 {
		return code
	}

	upToDate, err := gitutil.IsAncestor(dir, headSHA, targetSHA)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	if upToDate {
		// The head is already on the target: merged by hand and pushed, or
		// a merge whose ref update landed and whose record did not. Record
		// it rather than refuse, so a merge request cannot be stuck open
		// with no way to close it as merged (#108).
		if err := c.Store.MarkMerged(mr.ID, targetSHA, c.User.ID, ""); err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		c.Store.RecordEvent(repo.ID, c.User.ID, "mr.merged", fmt.Sprintf(`{"number":%d}`, mr.Number))
		return c.emit(map[string]any{"number": mr.Number, "strategy": "recorded", "sha": headSHA}, func(w io.Writer) {
			fmt.Fprintf(w, "%s already contains !%d; recorded as merged at %.10s\n", mr.TargetRef, mr.Number, headSHA)
		})
	}
	ffPossible, err := gitutil.IsAncestor(dir, targetSHA, headSHA)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}

	// Signature policy matrix: with require_signed_commits, only
	// fast-forward is allowed — squash, rebase-replay, and merge commits
	// are all server-created and unsigned, violating the branch's own
	// policy — and every landed commit must be verified. An explicit
	// rebase when fast-forward is already possible IS a fast-forward
	// (nothing is rewritten), so it stays legal.
	if repo.Settings.RequireSignedCommits {
		if strategy == "merge" || strategy == "squash" || !ffPossible {
			return c.fail(protocol.ExitDenied,
				"%s requires signed commits, so only fast-forward merges are allowed; rebase %s onto %s locally, re-push, and merge again",
				repo.Path(), mr.SourceRef, mr.TargetRef)
		}
		strategy = "ff"
		commits, err := gitutil.RevListRange(dir, targetSHA, headSHA)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		for _, sha := range commits {
			raw, err := gitutil.ReadCommit(dir, sha)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			parsed, err := sigParse(raw)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			res, err := VerifyCommitCached(c.Store, repo, parsed, sha)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			if res.State != "verified" {
				return c.fail(protocol.ExitDenied,
					"%s requires signed commits: %.10s is %s", repo.Path(), sha, res.State)
			}
		}
	}
	if strategy == "" {
		if ffPossible {
			strategy = "ff"
		} else {
			strategy = "merge"
		}
	}
	if strategy == "rebase" && ffPossible {
		// Nothing to rewrite: a rebase onto an ancestor is a fast-forward,
		// and taking it keeps the original commits and their signatures.
		strategy = "ff"
	}

	// Every server-created commit needs the merger's verified identity.
	mergerEmail := ""
	if strategy != "ff" {
		email, err := c.Store.PrimaryVerifiedEmail(c.User.ID)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		if email == "" {
			return c.fail(protocol.ExitDenied,
				"%s merges create commits carrying your identity: verify a primary email first (or use a fast-forward merge)", strategy)
		}
		mergerEmail = email
	}

	var newSHA string
	switch strategy {
	case "ff":
		if !ffPossible {
			return c.fail(protocol.ExitUsage,
				"fast-forward not possible: %s has diverged from the MR head; use --strategy merge or rebase and re-push", mr.TargetRef)
		}
		newSHA = headSHA

	case "merge":
		tree, conflict, err := gitutil.MergeTree(dir, targetSHA, headSHA)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		if conflict {
			return c.fail(protocol.ExitUsage,
				"merge conflicts between %s and the MR head; resolve locally and re-push", mr.TargetRef)
		}
		msg := fmt.Sprintf("Merge request !%d: %s\n\nMerged %s into %s", mr.Number, mr.Title, mr.SourceRef, mr.TargetRef)
		newSHA, err = gitutil.CommitTree(dir, tree, []string{targetSHA, headSHA}, c.User.Username, mergerEmail, msg)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}

	case "squash":
		// One new commit with the merged tree. Authorship credit goes to
		// the MR author (their verified identity when they have one); the
		// committer is the merger.
		tree := ""
		if ffPossible {
			t, err := gitutil.ResolveTree(dir, headSHA)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			tree = t
		} else {
			t, conflict, err := gitutil.MergeTree(dir, targetSHA, headSHA)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			if conflict {
				return c.fail(protocol.ExitUsage,
					"merge conflicts between %s and the MR head; resolve locally and re-push", mr.TargetRef)
			}
			tree = t
		}
		authorName, authorEmail := c.User.Username, mergerEmail
		if author, err := c.Store.UserByUsername(mr.Author); err == nil {
			if ae, err := c.Store.PrimaryVerifiedEmail(author.ID); err == nil && ae != "" {
				authorName, authorEmail = author.Username, ae
			}
		}
		msg := fmt.Sprintf("%s (!%d)", mr.Title, mr.Number)
		if mr.Body != "" {
			msg += "\n\n" + mr.Body
		}
		var err error
		newSHA, err = gitutil.CommitTreeIdent(dir, tree, []string{targetSHA},
			authorName, authorEmail, "", c.User.Username, mergerEmail, msg)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}

	case "rebase":
		commits, err := gitutil.RevListRange(dir, targetSHA, headSHA)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		// Oldest first.
		for i, j := 0, len(commits)-1; i < j; i, j = i+1, j-1 {
			commits[i], commits[j] = commits[j], commits[i]
		}
		onto := targetSHA
		for _, sha := range commits {
			parents, err := gitutil.CommitParents(dir, sha)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			if len(parents) > 1 {
				return c.fail(protocol.ExitUsage,
					"the MR contains merge commit %.10s; a rebase merge needs linear history — use --strategy merge or squash", sha)
			}
			base := onto // root commit: replay against the new tip itself
			if len(parents) == 1 {
				base = parents[0]
			}
			tree, conflict, err := gitutil.MergeTreeOnto(dir, base, onto, sha)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			if conflict {
				return c.fail(protocol.ExitUsage,
					"commit %.10s does not apply cleanly onto %s; rebase locally and re-push", sha, mr.TargetRef)
			}
			aName, aEmail, aDate, err := gitutil.AuthorIdent(dir, sha)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			msg, err := gitutil.CommitMessage(dir, sha)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
			onto, err = gitutil.CommitTreeIdent(dir, tree, []string{onto},
				aName, aEmail, aDate, c.User.Username, mergerEmail, msg)
			if err != nil {
				return c.fail(protocol.ExitFailure, "%v", err)
			}
		}
		newSHA = onto
	}

	// A stacked merge request's diff is against this branch. After a
	// fast-forward or merge commit the same commits are on the target and
	// its diff is unchanged there; after a squash or rebase they are not,
	// and the stack would carry this merge request's changes a second
	// time. Refuse rather than leave the stack wrong.
	var stack []store.MR
	if mr.SourceRepoID == repo.ID {
		stack, _ = c.Store.OpenMRsByTarget(repo.ID, mr.SourceRef)
	}
	if len(stack) > 0 && (strategy == "squash" || strategy == "rebase") {
		var nums []string
		for _, k := range stack {
			nums = append(nums, fmt.Sprintf("!%d", k.Number))
		}
		return c.fail(protocol.ExitUsage,
			"%s is stacked on by %s; a %s merge rewrites the commits they build on. Merge with --strategy ff or merge, or merge the stack into %s first",
			fmt.Sprintf("!%d", mr.Number), strings.Join(nums, ", "), strategy, mr.SourceRef)
	}

	// CAS so a concurrent push between our read and this write fails the
	// merge instead of silently discarding the push.
	if err := gitutil.UpdateRefCAS(dir, targetRef, newSHA, targetSHA); err != nil {
		return c.fail(protocol.ExitFailure, "target branch moved during merge; retry: %v", err)
	}
	if err := c.Store.MarkMerged(mr.ID, targetSHA, c.User.ID, ""); err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	c.Store.RecordEvent(repo.ID, c.User.ID, "mr.merged", fmt.Sprintf(`{"number":%d,"sha":%q}`, mr.Number, newSHA))
	// The stack moves up: whatever targeted this branch now targets what
	// it merged into, reviews intact, since that diff is the one they
	// were of.
	for _, k := range stack {
		if err := c.Store.RetargetKeepingReviews(k.ID, mr.TargetRef); err != nil {
			continue
		}
		c.Store.AddMRSystemComment(k.ID, c.User.ID, fmt.Sprintf("retargeted from %s to %s: !%d merged", mr.SourceRef, mr.TargetRef, mr.Number))
		if parts, err := c.Store.MRParticipants(k.ID); err == nil {
			notify(c, parts, notice{repo: repo, kind: "mr",
				subject: mrSubject(repo, k.Number, k.Title),
				action:  fmt.Sprintf("retargeted !%d from %s to %s: !%d merged", k.Number, mr.SourceRef, mr.TargetRef, mr.Number),
				path:    fmt.Sprintf("%s/mrs/%d", repo.Path(), k.Number)})
		}
	}
	// Merges bypass receive-pack, so the commit-message issue actions
	// (closes #N, references) run here for the newly landed commits. The
	// description is scanned after them, so a commit wins the attribution
	// when both name the same issue.
	if mr.TargetRef == repo.DefaultBranch {
		ProcessCommitMessages(c.Store, dir, repo, c.User.ID, targetSHA, newSHA)
		ProcessMRDescription(c.Store, repo, mr, c.User.ID)
		RecordLandedCommits(c.Store, dir, repo, targetSHA, newSHA)
	}
	// A merge moves the ref directly, so it never reaches post-receive and
	// none of the ref-update work fires on its own. The event webhooks
	// subscribe to, and the branch's CI jobs, happen here instead.
	c.Store.RecordEvent(repo.ID, c.User.ID, "push", fmt.Sprintf(
		`{"ref":%q,"old":%q,"new":%q,"forced":false,"deleted":false}`,
		targetRef, targetSHA, newSHA))
	QueueBranchBuilds(c.Store, c.Cfg.Server.Root, c.Cfg.Server.SiteURL,
		repo, c.User.ID, mr.TargetRef, newSHA, time.Now())
	c.Store.MarkMirrorsDirty(repo.ID, "push")
	if parts, err := c.Store.MRParticipants(mr.ID); err == nil {
		notify(c, parts, notice{repo: repo, kind: "mr",
			subject: mrSubject(repo, mr.Number, mr.Title),
			action:  fmt.Sprintf("merged !%d into %s (%s)", mr.Number, mr.TargetRef, strategy),
			path:    fmt.Sprintf("%s/mrs/%d", repo.Path(), mr.Number)})
	}
	return c.emit(map[string]any{"number": mr.Number, "strategy": strategy, "sha": newSHA}, func(w io.Writer) {
		fmt.Fprintf(w, "merged %s!%d into %s (%s) at %.10s\n", repo.Path(), mr.Number, mr.TargetRef, strategy, newSHA)
	})
}

// reviewGates enforces require_approvals (fresh, non-author, latest review
// per reviewer; a fresh request-changes blocks), require_codeowners, and
// require_resolved. Returns -1 to proceed.
func (c *Ctx) reviewGates(repo store.Repo, mr store.MR, dir, targetSHA, headSHA string) int {
	// A draft is open but not asking. This gate is unconditional — no
	// setting turns it off — because the author said so themselves.
	if mr.Draft {
		return c.fail(protocol.ExitDenied,
			"!%d is a draft; `gitbay mr ready %s %d` first", mr.Number, repo.Path(), mr.Number)
	}
	set := repo.Settings
	reviews, err := c.Store.ListMRReviews(mr.ID)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	// Latest fresh review per reviewer decides their stance — but only
	// from someone the repository trusts to write to it. Reviewing is
	// open to any reader, which is what makes an outside opinion on a
	// public change possible; deciding a merge gate is not the same
	// thing, and counting every verdict let anyone with an account
	// satisfy require_approvals or block a merge indefinitely (#147).
	counts := ReviewersWhoCount(c.Store, repo, reviews)
	latest := map[string]string{}
	for _, r := range reviews {
		if r.Stale || r.Reviewer == mr.Author || !counts[r.Reviewer] {
			continue
		}
		latest[r.Reviewer] = r.Verdict
	}
	var approvers []string
	var blockers []string
	for who, verdict := range latest {
		switch verdict {
		case "approve":
			approvers = append(approvers, who)
		case "request_changes":
			blockers = append(blockers, who)
		}
	}

	if set.RequireApprovals > 0 {
		if len(blockers) > 0 {
			slices.Sort(blockers)
			return c.fail(protocol.ExitDenied,
				"%s requested changes on !%d; resolve their review before merging", strings.Join(blockers, ", "), mr.Number)
		}
		if len(approvers) < set.RequireApprovals {
			return c.fail(protocol.ExitDenied,
				"%s requires %d fresh approval(s); !%d has %d", repo.Path(), set.RequireApprovals, mr.Number, len(approvers))
		}
	}

	// CODEOWNERS: every owned changed file needs an approval from one of
	// its owners. require_codeowners is the opt-in — a repository can
	// carry the file as documentation of who to ask without it gating
	// merges — and it does not wait on require_approvals (#99).
	if set.RequireCodeowners {
		content, err := gitutil.ReadBlob(dir, "refs/heads/"+mr.TargetRef, "CODEOWNERS", 1<<20)
		if err != nil {
			content, err = gitutil.ReadBlob(dir, "refs/heads/"+mr.TargetRef, ".gitbay/CODEOWNERS", 1<<20)
		}
		if err != nil || len(content) == 0 {
			return c.fail(protocol.ExitDenied,
				"%s requires CODEOWNERS approval but %s carries no CODEOWNERS file",
				repo.Path(), mr.TargetRef)
		}
		rules := policy.ParseCodeowners(string(content))
		base, err := gitutil.MergeBase(dir, targetSHA, headSHA)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		files, err := gitutil.DiffFiles(dir, base, headSHA)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		approved := map[string]bool{}
		for _, a := range approvers {
			approved[a] = true
		}
		missing := map[string][]string{} // owner-set key -> example paths
		for _, f := range files {
			owners := policy.OwnersFor(rules, f)
			if owners == nil {
				continue
			}
			ok := false
			for _, o := range owners {
				if approved[o] {
					ok = true
					break
				}
			}
			if !ok {
				key := strings.Join(owners, ",")
				if len(missing[key]) < 3 {
					missing[key] = append(missing[key], f)
				}
			}
		}
		if len(missing) > 0 {
			var parts []string
			for owners, paths := range missing {
				parts = append(parts, fmt.Sprintf("%s (owned by %s)", strings.Join(paths, ", "), owners))
			}
			slices.Sort(parts)
			return c.fail(protocol.ExitDenied,
				"CODEOWNERS approval missing for: %s", strings.Join(parts, "; "))
		}
	}

	if set.RequireResolved {
		n, err := c.Store.UnresolvedThreadCount(mr.ID)
		if err != nil {
			return c.fail(protocol.ExitFailure, "%v", err)
		}
		if n > 0 {
			return c.fail(protocol.ExitDenied,
				"%s requires review threads resolved; !%d has %d open (mr threads %s %d)", repo.Path(), mr.Number, n, repo.Path(), mr.Number)
		}
	}
	return -1
}

func runMRDraft(c *Ctx, args []string) int { return setMRDraft(c, args, true) }
func runMRReady(c *Ctx, args []string) int { return setMRDraft(c, args, false) }

func setMRDraft(c *Ctx, args []string, draft bool) int {
	verb := "ready"
	if draft {
		verb = "draft"
	}
	repo, mr, code := mrRef(c, args, policy.CanRead)
	if code >= 0 {
		return code
	}
	if code := refuseArchived(c, repo); code >= 0 {
		return code
	}
	if len(args) != 2 {
		return c.fail(protocol.ExitUsage, "usage: mr %s <owner/name> <n>", verb)
	}
	if code := authorOrWrite(c, repo, mr.Author, "change this merge request"); code >= 0 {
		return code
	}
	if mr.State != "open" && mr.State != "source_gone" {
		return c.fail(protocol.ExitUsage, "MR !%d is %s", mr.Number, mr.State)
	}
	if mr.Draft == draft {
		state := "already ready"
		if draft {
			state = "already a draft"
		}
		return c.fail(protocol.ExitUsage, "MR !%d is %s", mr.Number, state)
	}
	if err := c.Store.SetMRDraft(mr.ID, draft); err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	c.Store.RecordEvent(repo.ID, c.User.ID, "mr.draft",
		fmt.Sprintf(`{"number":%d,"draft":%t}`, mr.Number, draft))
	// Marking ready is the request for review; going back to draft
	// withdraws it and is not worth anyone's inbox.
	//
	// The targets are the repository's, not the thread's participants.
	// Until someone comments or reviews, the only participant is the
	// author, who is the actor and excluded — so notifying participants
	// here reaches nobody, which is exactly what opening it as a draft
	// and then marking it ready would do. Opening a merge request tells
	// the repository; so does saying it is finally asking.
	if !draft {
		if targets, err := c.Store.RepoNotifyTargets(repo); err == nil {
			parts, _ := c.Store.MRParticipants(mr.ID)
			notify(c, append(targets, parts...), notice{repo: repo, kind: "mr",
				subject: mrSubject(repo, mr.Number, mr.Title),
				action:  fmt.Sprintf("marked !%d ready for review", mr.Number),
				path:    fmt.Sprintf("%s/mrs/%d", repo.Path(), mr.Number)})
		}
	}
	return c.emit(map[string]any{"number": mr.Number, "draft": draft}, func(w io.Writer) {
		fmt.Fprintf(w, "%s!%d is %s\n", repo.Path(), mr.Number, map[bool]string{true: "a draft", false: "ready"}[draft])
	})
}

func runMRClose(c *Ctx, args []string) int {
	repo, mr, code := mrRef(c, args, policy.CanRead)
	if code >= 0 {
		return code
	}
	if code := refuseArchived(c, repo); code >= 0 {
		return code
	}
	if len(args) != 2 {
		return c.fail(protocol.ExitUsage, "usage: mr close <owner/name> <n>")
	}
	if code := authorOrWrite(c, repo, mr.Author, "close this merge request"); code >= 0 {
		return code
	}
	if mr.State == "merged" || mr.State == "closed" {
		return c.fail(protocol.ExitUsage, "MR !%d is already %s", mr.Number, mr.State)
	}
	if err := c.Store.MarkClosed(mr.ID, c.User.ID, ""); err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	c.Store.RecordEvent(repo.ID, c.User.ID, "mr.closed", fmt.Sprintf(`{"number":%d}`, mr.Number))
	if parts, err := c.Store.MRParticipants(mr.ID); err == nil {
		notify(c, parts, notice{repo: repo, kind: "mr",
			subject: mrSubject(repo, mr.Number, mr.Title),
			action:  fmt.Sprintf("closed !%d", mr.Number),
			path:    fmt.Sprintf("%s/mrs/%d", repo.Path(), mr.Number)})
	}
	return c.emit(map[string]any{"number": mr.Number, "state": "closed"}, func(w io.Writer) {
		fmt.Fprintf(w, "closed %s!%d\n", repo.Path(), mr.Number)
	})
}

// reviewAction is what a review notification says it was. A verdict with
// a batch behind it is a different thing from a bare verdict, and the
// person reading the mail is deciding whether to open it.
func reviewAction(number int64, verdict string, published int64) string {
	if published > 0 {
		return fmt.Sprintf("reviewed !%d: %s, with %d comment(s)", number, verdict, published)
	}
	return fmt.Sprintf("reviewed !%d: %s", number, verdict)
}

// RevisionOut is one head a merge request has had.
type RevisionOut struct {
	N         int    `json:"n"` // 1 is the first push
	SHA       string `json:"sha"`
	BaseSHA   string `json:"base_sha,omitempty"`
	CreatedAt string `json:"created_at"`
	Current   bool   `json:"current,omitempty"`
}

func mrRevisions(c *Ctx, mr store.MR) ([]RevisionOut, error) {
	heads, err := c.Store.MRHeads(mr.ID)
	if err != nil {
		return nil, err
	}
	out := make([]RevisionOut, 0, len(heads))
	for i, h := range heads {
		out = append(out, RevisionOut{N: i + 1, SHA: h.SHA, BaseSHA: h.BaseSHA,
			CreatedAt: h.CreatedAt, Current: h.SHA == mr.HeadSHA})
	}
	return out, nil
}

func runMRRevisions(c *Ctx, args []string) int {
	repo, mr, code := mrRef(c, args, policy.CanRead)
	if code >= 0 {
		return code
	}
	if len(args) != 2 {
		return c.fail(protocol.ExitUsage, "usage: mr revisions <owner/name> <n>")
	}
	revs, err := mrRevisions(c, mr)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	return c.emit(revs, func(w io.Writer) {
		for _, r := range revs {
			mark := " "
			if r.Current {
				mark = "*"
			}
			fmt.Fprintf(w, "%s v%d\t%.10s\t%s\n", mark, r.N, r.SHA, r.CreatedAt)
		}
		if len(revs) < 2 {
			fmt.Fprintf(w, "\nonly one revision; %s!%d has not been pushed to since it was opened\n",
				repo.Path(), mr.Number)
		}
	})
}

func runMRRangeDiff(c *Ctx, args []string) int {
	const usage = "mr range-diff <owner/name> <n> [--from <sha>] [--to <sha>]"
	f, err := parseFlags(args, flagSpec{Values: []string{"--from", "--to"}, MaxPos: 2, Usage: usage})
	if err != nil {
		return c.fail(protocol.ExitUsage, "%v", err)
	}
	repo, mr, code := mrRef(c, f.Pos, policy.CanRead)
	if code >= 0 {
		return code
	}
	if len(f.Pos) != 2 {
		return c.fail(protocol.ExitUsage, "usage: %s", usage)
	}
	revs, err := mrRevisions(c, mr)
	if err != nil {
		return c.fail(protocol.ExitFailure, "%v", err)
	}
	// One revision is a merge request nobody has pushed to since it was
	// opened. The argv was fine and the answer is "nothing changed", so
	// this succeeds with an empty patch rather than failing.
	if len(revs) < 2 {
		fmt.Fprintf(c.Stderr, "%s!%d has one revision; nothing to compare it against\n",
			repo.Path(), mr.Number)
		return protocol.ExitOK
	}
	// Default to the two most recent, which is "what changed since the
	// last push" — the question a stale review asks.
	from, to := revs[len(revs)-2], revs[len(revs)-1]
	pick := func(sha string) (RevisionOut, bool) {
		for _, r := range revs {
			if strings.HasPrefix(r.SHA, sha) {
				return r, true
			}
		}
		return RevisionOut{}, false
	}
	if v := f.Value("--from"); v != "" {
		r, ok := pick(v)
		if !ok {
			return c.fail(protocol.ExitNotFound, "%.12s is not a revision of !%d; see `mr revisions`", v, mr.Number)
		}
		from = r
	}
	if v := f.Value("--to"); v != "" {
		r, ok := pick(v)
		if !ok {
			return c.fail(protocol.ExitNotFound, "%.12s is not a revision of !%d; see `mr revisions`", v, mr.Number)
		}
		to = r
	}
	if from.SHA == to.SHA {
		return c.fail(protocol.ExitUsage, "--from and --to are the same revision")
	}

	dir := RepoDir(c.Cfg.Server.Root, repo.OwnerName, repo.Name)
	// A revision recorded before its base could be worked out, or by a
	// migration backfill, falls back to the target's merge base.
	baseOf := func(r RevisionOut) string {
		if r.BaseSHA != "" {
			return r.BaseSHA
		}
		b, err := gitutil.MergeBase(dir, "refs/heads/"+mr.TargetRef, r.SHA)
		if err != nil {
			return r.SHA + "^"
		}
		return b
	}
	patch, truncated, err := gitutil.RangeDiff(dir, baseOf(from), from.SHA, baseOf(to), to.SHA, 4<<20)
	if err != nil {
		return c.fail(protocol.ExitFailure,
			"%v (the objects for an older revision may have been garbage-collected)", err)
	}
	fmt.Fprint(c.Stdout, patch)
	if truncated {
		fmt.Fprintln(c.Stderr, "range-diff truncated at 4 MiB")
	}
	return protocol.ExitOK
}

// reviewersWhoCount is the set of reviewers whose verdict decides a merge
// gate: those with write access to the repository.
//
// Write, rather than a separate reviewer role, because it is the same
// question the gates already answer — a person who could push this change
// themselves is the person whose approval means the repository accepts
// it. Someone named in CODEOWNERS without write is a misconfiguration the
// owner should fix rather than a case to special-case here: they could
// not merge what they approved.
// Exported because the web renders the same distinction: a page that
// showed an approval the gate ignores would differ from the gate, and the
// difference would only surface when a merge was refused.
func ReviewersWhoCount(st *store.Store, repo store.Repo, reviews []store.MRReview) map[string]bool {
	counts := map[string]bool{}
	for _, r := range reviews {
		if _, done := counts[r.Reviewer]; done {
			continue
		}
		counts[r.Reviewer] = false
		u, err := st.UserByUsername(r.Reviewer)
		if err != nil {
			continue
		}
		grant, err := st.AccessRole(repo.ID, u.ID)
		if err != nil {
			continue
		}
		counts[r.Reviewer] = policy.CanWrite(u, repo, grant)
	}
	return counts
}