package store

import (
	"database/sql"
	"errors"
	"strings"
)

type MR struct {
	ID           int64
	RepoID       int64
	Number       int64
	Author       string
	SourceRepoID int64  // 0 when the source repo is gone
	SourcePath   string // owner/name of source repo, "" when gone
	SourceRef    string
	TargetRef    string
	Title        string
	Body         string
	BodyFormat   string // md | org
	State        string // open | merged | closed | source_gone
	// Draft marks an open merge request that is not asking to be merged
	// yet. Not a state: see migration 0037.
	Draft      bool
	Milestone  string
	HeadSHA    string
	MergedBase string // target tip at merge time; base for historical diffs
	MergedAt   string // "" unless merged
	MergedBy   string // "" when unknown (imports) or the account is gone
	ClosedAt   string // "" unless closed without merging
	ClosedBy   string
	// SupersededBy is the number, within this repository, of the merge
	// request this one was closed in favour of. 0 means none.
	SupersededBy int64
	CreatedAt    string
	UpdatedAt    string
	Labels       []string
	// ReviewRequests is who has been asked, directly, for a review — the
	// mr review request counterpart of Issue.Assignees.
	ReviewRequests []string
	// The queued merge (mr merge --when-ready); QueuedAt is "" when there
	// is none. QueueReason is why the last attempt did not merge.
	QueuedByID    int64
	QueuedBy      string
	QueueStrategy string
	QueueReason   string
	QueuedAt      string
}

type MRReview struct {
	Reviewer  string
	Verdict   string
	HeadSHA   string
	Stale     bool
	CreatedAt string
}

func (s *Store) CreateMR(repoID, authorID, sourceRepoID int64, sourceRef, targetRef, title, body, headSHA, format string, draft bool) (int64, error) {
	tx, err := s.DB.Begin()
	if err != nil {
		return 0, err
	}
	defer tx.Rollback()
	if _, err := tx.Exec("UPDATE repos SET mr_counter = mr_counter + 1 WHERE id = ?", repoID); err != nil {
		return 0, err
	}
	var n int64
	if err := tx.QueryRow("SELECT mr_counter FROM repos WHERE id = ?", repoID).Scan(&n); err != nil {
		return 0, err
	}
	if _, err := tx.Exec(`
		INSERT INTO merge_requests (repo_id, number, author_id, source_repo_id, source_ref, target_ref, title, body, head_sha, body_format, draft)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		repoID, n, authorID, sourceRepoID, sourceRef, targetRef, title, body, headSHA, format, draft); err != nil {
		return 0, err
	}
	if headSHA != "" {
		var mrID int64
		if err := tx.QueryRow("SELECT id FROM merge_requests WHERE repo_id = ? AND number = ?",
			repoID, n).Scan(&mrID); err != nil {
			return 0, err
		}
		if _, err := tx.Exec("INSERT INTO mr_heads (mr_id, sha) VALUES (?, ?)", mrID, headSHA); err != nil {
			return 0, err
		}
	}
	return n, tx.Commit()
}

// SetMRDraft marks an open merge request as a draft, or takes the mark
// off. Merging is refused while it is set.
func (s *Store) SetMRDraft(mrID int64, draft bool) error {
	_, err := s.DB.Exec(
		"UPDATE merge_requests SET draft = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now') WHERE id = ?",
		draft, mrID)
	return err
}

const mrSelect = `
	SELECT m.id, m.repo_id, m.number, u.username,
	       COALESCE(m.source_repo_id, 0),
	       COALESCE(COALESCE(su.username, so.name) || '/' || sr.name, ''),
	       m.source_ref, m.target_ref, m.title, m.body, m.body_format, m.state, m.draft,
	       COALESCE(ms.title, ''), m.head_sha,
	       m.merged_base, m.merged_at, COALESCE(mu.username, ''),
	       m.closed_at, COALESCE(cu.username, ''), COALESCE(m.superseded_by, 0), m.created_at, m.updated_at,
	       COALESCE(q.user_id, 0), COALESCE(qu.username, ''), COALESCE(q.strategy, ''),
	       COALESCE(q.reason, ''), COALESCE(q.queued_at, '')
	FROM merge_requests m
	JOIN users u ON u.id = m.author_id
	LEFT JOIN users mu ON mu.id = m.merged_by
	LEFT JOIN users cu ON cu.id = m.closed_by
	LEFT JOIN repos sr ON sr.id = m.source_repo_id
	LEFT JOIN users su ON sr.owner_kind = 'user' AND su.id = sr.owner_id
	LEFT JOIN orgs so  ON sr.owner_kind = 'org'  AND so.id = sr.owner_id
	LEFT JOIN milestones ms ON ms.id = m.milestone_id
	LEFT JOIN mr_merge_queue q ON q.mr_id = m.id
	LEFT JOIN users qu ON qu.id = q.user_id`

func scanMR(row interface{ Scan(...any) error }) (MR, error) {
	var m MR
	err := row.Scan(&m.ID, &m.RepoID, &m.Number, &m.Author, &m.SourceRepoID, &m.SourcePath,
		&m.SourceRef, &m.TargetRef, &m.Title, &m.Body, &m.BodyFormat, &m.State, &m.Draft, &m.Milestone, &m.HeadSHA, &m.MergedBase,
		&m.MergedAt, &m.MergedBy, &m.ClosedAt, &m.ClosedBy, &m.SupersededBy, &m.CreatedAt, &m.UpdatedAt,
		&m.QueuedByID, &m.QueuedBy, &m.QueueStrategy, &m.QueueReason, &m.QueuedAt)
	return m, err
}

func (s *Store) MRByNumber(repoID, number int64) (MR, error) {
	m, err := scanMR(s.DB.QueryRow(mrSelect+" WHERE m.repo_id = ? AND m.number = ?", repoID, number))
	if errors.Is(err, sql.ErrNoRows) {
		return m, ErrNotFound
	}
	if err != nil {
		return m, err
	}
	if m.Labels, err = s.issueStrings(m.ID, `
		SELECT l.name FROM mr_labels ml JOIN labels l ON l.id = ml.label_id
		WHERE ml.mr_id = ? ORDER BY l.name`); err != nil {
		return m, err
	}
	m.ReviewRequests, err = s.issueStrings(m.ID, `
		SELECT u.username FROM mr_review_requests rr JOIN users u ON u.id = rr.user_id
		WHERE rr.mr_id = ? ORDER BY u.username`)
	return m, err
}

// ListMRLabels returns the label names attached to each merge request of
// a repo, keyed by merge request id, its org's labels included. Used by
// the web merge request listing; ListMRs itself stays label-free for the
// CLI's lean list output.
func (s *Store) ListMRLabels(repo Repo) (map[int64][]string, error) {
	return s.listItemLabels(mrLabelJoin, repo)
}

// SetMRLabel attaches (add) or detaches a label by name, the issue rules
// exactly: the org's row when the org has the name, else the
// repository's, created on first use.
func (s *Store) SetMRLabel(repo Repo, mrID int64, name string, add bool) error {
	return s.setItemLabel(mrLabelJoin, repo, mrID, name, add)
}

// SetMRReviewRequest adds or removes a review request by user id — the
// mr review request counterpart of SetIssueAssignee.
func (s *Store) SetMRReviewRequest(mrID, userID int64, add bool) error {
	if add {
		_, err := s.DB.Exec(
			"INSERT INTO mr_review_requests (mr_id, user_id) VALUES (?, ?) ON CONFLICT DO NOTHING",
			mrID, userID)
		return err
	}
	res, err := s.DB.Exec(
		"DELETE FROM mr_review_requests WHERE mr_id = ? AND user_id = ?", mrID, userID)
	if err != nil {
		return err
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return ErrNotFound
	}
	return nil
}

// MRReviewRequestIDs returns who has been asked for a review, by id — for
// notifying them without a username round trip.
func (s *Store) MRReviewRequestIDs(mrID int64) ([]int64, error) {
	return s.idQuery("SELECT user_id FROM mr_review_requests WHERE mr_id = ?", mrID)
}

// ListMRs returns merge requests for a repo. limit 0 means everything;
// before (an MR number) starts the page strictly below it, matching the
// number-descending order.
// MRFilter narrows a listing. Empty strings match anything; State "all"
// too. Milestone "none" selects merge requests with no milestone.
type MRFilter struct {
	State     string
	Label     string
	Author    string
	Milestone string
	Search    string // full-text over title and body
	Limit     int
	Before    int64
}

func (s *Store) ListMRs(repoID int64, state string, limit int, before int64) ([]MR, error) {
	return s.QueryMRs(repoID, MRFilter{State: state, Limit: limit, Before: before})
}

// QueryMRs lists a repository's merge requests, newest first, narrowed
// by f.
func (s *Store) QueryMRs(repoID int64, f MRFilter) ([]MR, error) {
	q := mrSelect + " WHERE m.repo_id = ?"
	args := []any{repoID}
	if f.State != "" && f.State != "all" {
		q += " AND m.state = ?"
		args = append(args, f.State)
	}
	if f.Label != "" {
		q += ` AND EXISTS (SELECT 1 FROM mr_labels ml JOIN labels l ON l.id = ml.label_id
			WHERE ml.mr_id = m.id AND l.name = ?)`
		args = append(args, f.Label)
	}
	if f.Author != "" {
		q += " AND u.username = ?"
		args = append(args, f.Author)
	}
	switch f.Milestone {
	case "":
	case "none":
		q += " AND m.milestone_id IS NULL"
	default:
		q += " AND ms.title = ?"
		args = append(args, f.Milestone)
	}
	if f.Search != "" {
		q += " AND m.id IN (SELECT rowid FROM mr_fts WHERE mr_fts MATCH ?)"
		args = append(args, FTSQuery(f.Search))
	}
	if f.Before > 0 {
		q += " AND m.number < ?"
		args = append(args, f.Before)
	}
	q += " ORDER BY m.number DESC"
	if f.Limit > 0 {
		q += " LIMIT ?"
		args = append(args, f.Limit)
	}
	rows, err := s.DB.Query(q, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []MR
	for rows.Next() {
		m, err := scanMR(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

// OpenMRsBySource returns open (and source_gone) MRs fed by the given source
// repo branch — the cross-repo hook effect consults this.
func (s *Store) OpenMRsBySource(sourceRepoID int64, sourceRef string) ([]MR, error) {
	rows, err := s.DB.Query(
		mrSelect+" WHERE m.source_repo_id = ? AND m.source_ref = ? AND m.state IN ('open','source_gone')",
		sourceRepoID, sourceRef)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []MR
	for rows.Next() {
		m, err := scanMR(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

// MarkMerged records the merge along with the target tip it landed on, so
// the MR's diff stays reconstructable after fast-forwards. actorID 0 and an
// empty at leave the merger unknown and stamp the current time, which is
// what an import that carries neither can say.
func (s *Store) MarkMerged(mrID int64, baseSHA string, actorID int64, at string) error {
	_, err := s.DB.Exec(
		`UPDATE merge_requests SET state = 'merged', merged_base = ?,
			merged_at = COALESCE(NULLIF(?, ''), strftime('%Y-%m-%dT%H:%M:%fZ','now')),
			merged_by = NULLIF(?, 0),
			updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now') WHERE id = ?`,
		baseSHA, at, actorID, mrID)
	return err
}

// MarkClosed is MarkMerged's counterpart for a merge request closed without
// merging.
func (s *Store) MarkClosed(mrID, actorID int64, at string) error {
	_, err := s.DB.Exec(
		`UPDATE merge_requests SET state = 'closed',
			closed_at = COALESCE(NULLIF(?, ''), strftime('%Y-%m-%dT%H:%M:%fZ','now')),
			closed_by = NULLIF(?, 0),
			updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now') WHERE id = ?`,
		at, actorID, mrID)
	return err
}

// SetSupersededBy records which merge request, by number within the same
// repository, this one was closed in favour of. n of 0 clears it.
func (s *Store) SetSupersededBy(mrID, n int64) error {
	var v any
	if n != 0 {
		v = n
	}
	_, err := s.DB.Exec("UPDATE merge_requests SET superseded_by = ? WHERE id = ?", v, mrID)
	return err
}

// MRsSuperseding returns the merge requests in a repository whose
// superseded_by names number, oldest first — the reverse of
// MR.SupersededBy.
func (s *Store) MRsSuperseding(repoID, number int64) ([]MR, error) {
	rows, err := s.DB.Query(mrSelect+" WHERE m.repo_id = ? AND m.superseded_by = ? ORDER BY m.number ASC", repoID, number)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []MR
	for rows.Next() {
		m, err := scanMR(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

// SetMRState moves an MR between states that carry no resolution stamp.
// Returning to open (a source branch that came back) clears one.
func (s *Store) SetMRState(mrID int64, state string) error {
	stamp := ""
	if state == "open" || state == "source_gone" {
		stamp = ", merged_at = '', merged_by = NULL, closed_at = '', closed_by = NULL"
	}
	res, err := s.DB.Exec(
		"UPDATE merge_requests SET state = ?"+stamp+", updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now') WHERE id = ?",
		state, mrID)
	if err != nil {
		return err
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return ErrNotFound
	}
	return nil
}

// UpdateMRHead moves a merge request onto a new head, stales the reviews
// of the old one, and records the head in the history a range-diff reads.
// baseSHA is the merge base at this moment; "" when the caller could not
// work it out, which only costs the range-diff its precision.
//
// sameDiff says the new head proposes the change the old one did (a
// rebase onto a moved target, or the same commits pushed again). Then the
// fresh reviews of the old head are reviews of this diff and move to the
// new head rather than going stale (#198). Reviews already stale stay so.
func (s *Store) UpdateMRHead(mrID int64, headSHA, baseSHA string, sameDiff bool) error {
	tx, err := s.DB.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	if sameDiff {
		if _, err := tx.Exec(`
			UPDATE mr_reviews SET head_sha = ? WHERE mr_id = ? AND stale = 0
			AND head_sha = (SELECT head_sha FROM merge_requests WHERE id = ?)`,
			headSHA, mrID, mrID); err != nil {
			return err
		}
	}
	if _, err := tx.Exec(
		"UPDATE merge_requests SET head_sha = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now') WHERE id = ?",
		headSHA, mrID); err != nil {
		return err
	}
	if _, err := tx.Exec(
		"UPDATE mr_reviews SET stale = 1 WHERE mr_id = ? AND head_sha <> ?", mrID, headSHA); err != nil {
		return err
	}
	// Same head twice is a push that changed nothing about this merge
	// request; it should not add a revision to compare against.
	var last string
	tx.QueryRow("SELECT sha FROM mr_heads WHERE mr_id = ? ORDER BY id DESC LIMIT 1", mrID).Scan(&last)
	if last != headSHA {
		if _, err := tx.Exec(
			"INSERT INTO mr_heads (mr_id, sha, base_sha) VALUES (?, ?, ?)", mrID, headSHA, baseSHA); err != nil {
			return err
		}
	}
	return tx.Commit()
}

// MRHead is one revision a merge request has had.
type MRHead struct {
	SHA       string
	BaseSHA   string
	CreatedAt string
}

// MRHeads returns a merge request's revisions, oldest first.
func (s *Store) MRHeads(mrID int64) ([]MRHead, error) {
	rows, err := s.DB.Query(
		"SELECT sha, base_sha, created_at FROM mr_heads WHERE mr_id = ? ORDER BY id", mrID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []MRHead
	for rows.Next() {
		var h MRHead
		if err := rows.Scan(&h.SHA, &h.BaseSHA, &h.CreatedAt); err != nil {
			return nil, err
		}
		out = append(out, h)
	}
	return out, rows.Err()
}

// SetMRTarget retargets a merge request and marks every existing review
// stale, in one transaction. The base of the diff is derived from the
// target on every read, so nothing else has to move; an approval,
// though, was of the diff against the old branch.
func (s *Store) SetMRTarget(mrID int64, targetRef string) error {
	tx, err := s.DB.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	res, err := tx.Exec(
		"UPDATE merge_requests SET target_ref = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now') WHERE id = ?",
		targetRef, mrID)
	if err != nil {
		return err
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return ErrNotFound
	}
	if _, err := tx.Exec("UPDATE mr_reviews SET stale = 1 WHERE mr_id = ?", mrID); err != nil {
		return err
	}
	return tx.Commit()
}

// MarkSourceGoneForRepo flags every open MR sourced from the repo; called
// when a fork is deleted. Head refs in the target repos are retained.
func (s *Store) MarkSourceGoneForRepo(sourceRepoID int64) error {
	_, err := s.DB.Exec(
		"UPDATE merge_requests SET state = 'source_gone', updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now') WHERE source_repo_id = ? AND state = 'open'",
		sourceRepoID)
	return err
}

func (s *Store) AddMRComment(mrID, authorID int64, body, format string) error {
	_, err := s.DB.Exec(
		"INSERT INTO mr_comments (mr_id, author_id, body, body_format) VALUES (?, ?, ?, ?)",
		mrID, authorID, body, format)
	return err
}

// UpdateMRText edits title, body, and/or markup format; nil leaves a field
// unchanged.
func (s *Store) UpdateMRText(mrID int64, title, body, format *string) error {
	set, args := []string{}, []any{}
	if title != nil {
		set, args = append(set, "title = ?"), append(args, *title)
	}
	if body != nil {
		set, args = append(set, "body = ?"), append(args, *body)
	}
	if format != nil {
		set, args = append(set, "body_format = ?"), append(args, *format)
	}
	if len(set) == 0 {
		return nil
	}
	set = append(set, "updated_at = strftime('%Y-%m-%dT%H:%M:%fZ','now')")
	args = append(args, mrID)
	res, err := s.DB.Exec("UPDATE merge_requests SET "+strings.Join(set, ", ")+" WHERE id = ?", args...)
	if err != nil {
		return err
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return ErrNotFound
	}
	return nil
}

// AddMRSystemComment is the informational counterpart of AddMRComment.
func (s *Store) AddMRSystemComment(mrID, actorID int64, body string) error {
	_, err := s.DB.Exec(
		"INSERT INTO mr_comments (mr_id, author_id, body, kind) VALUES (?, ?, ?, 'system')",
		mrID, actorID, body)
	return err
}

func (s *Store) ListMRComments(mrID int64) ([]IssueComment, error) {
	rows, err := s.DB.Query(`
		SELECT c.id, CASE WHEN c.kind = 'system' THEN 'system' ELSE u.username END,
		       c.body, c.body_format, c.created_at, c.kind
		FROM mr_comments c JOIN users u ON u.id = c.author_id
		WHERE c.mr_id = ? ORDER BY c.id`, mrID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []IssueComment
	for rows.Next() {
		var c IssueComment
		if err := rows.Scan(&c.ID, &c.Author, &c.Body, &c.BodyFormat, &c.CreatedAt, &c.Kind); err != nil {
			return nil, err
		}
		out = append(out, c)
	}
	return out, rows.Err()
}

// MRCommentCounts totals, per MR, conversation comments plus diff-thread
// roots — what the list page shows as one comment count. System comments,
// diff-thread replies, and pending (unpublished) diff comments do not
// count. The list handler asks for every row on a page in one call rather
// than one query per MR.
func (s *Store) MRCommentCounts(repoID int64, mrIDs []int64) (map[int64]int, error) {
	out := map[int64]int{}
	if len(mrIDs) == 0 {
		return out, nil
	}
	ph := "?" + strings.Repeat(",?", len(mrIDs)-1)
	args := make([]any, 0, len(mrIDs)+1)
	args = append(args, repoID)
	for _, id := range mrIDs {
		args = append(args, id)
	}
	add := func(query string) error {
		rows, err := s.DB.Query(query, args...)
		if err != nil {
			return err
		}
		defer rows.Close()
		for rows.Next() {
			var mrID int64
			var n int
			if err := rows.Scan(&mrID, &n); err != nil {
				return err
			}
			out[mrID] += n
		}
		return rows.Err()
	}
	if err := add(`
		SELECT c.mr_id, COUNT(*) FROM mr_comments c
		JOIN merge_requests m ON m.id = c.mr_id
		WHERE m.repo_id = ? AND c.kind <> 'system' AND c.mr_id IN (` + ph + `)
		GROUP BY c.mr_id`); err != nil {
		return nil, err
	}
	if err := add(`
		SELECT c.mr_id, COUNT(*) FROM mr_diff_comments c
		JOIN merge_requests m ON m.id = c.mr_id
		WHERE m.repo_id = ? AND c.reply_to IS NULL AND c.pending = 0 AND c.mr_id IN (` + ph + `)
		GROUP BY c.mr_id`); err != nil {
		return nil, err
	}
	return out, nil
}

func (s *Store) AddMRReview(mrID, reviewerID int64, verdict, headSHA string) error {
	_, err := s.DB.Exec(
		"INSERT INTO mr_reviews (mr_id, reviewer_id, verdict, head_sha) VALUES (?, ?, ?, ?)",
		mrID, reviewerID, verdict, headSHA)
	return err
}

func (s *Store) ListMRReviews(mrID int64) ([]MRReview, error) {
	rows, err := s.DB.Query(`
		SELECT u.username, r.verdict, r.head_sha, r.stale, r.created_at
		FROM mr_reviews r JOIN users u ON u.id = r.reviewer_id
		WHERE r.mr_id = ? ORDER BY r.id`, mrID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []MRReview
	for rows.Next() {
		var r MRReview
		var stale int
		if err := rows.Scan(&r.Reviewer, &r.Verdict, &r.HeadSHA, &stale, &r.CreatedAt); err != nil {
			return nil, err
		}
		r.Stale = stale != 0
		out = append(out, r)
	}
	return out, rows.Err()
}

// PrimaryVerifiedEmail returns the user's primary email if verified, else "".
func (s *Store) PrimaryVerifiedEmail(userID int64) (string, error) {
	var addr string
	err := s.DB.QueryRow(
		"SELECT address FROM emails WHERE user_id = ? AND is_primary = 1 AND verified_at IS NOT NULL",
		userID).Scan(&addr)
	if errors.Is(err, sql.ErrNoRows) {
		return "", nil
	}
	return addr, err
}

// ActivityMailAddress returns where activity mail for an account goes:
// its verified primary address, or "" when there is none or the account
// turned activity mail off (#194).
func (s *Store) ActivityMailAddress(userID int64) (string, error) {
	on, err := s.MailEnabled(userID)
	if err != nil || !on {
		return "", err
	}
	return s.PrimaryVerifiedEmail(userID)
}

// PreferredVerifiedEmail returns the primary address if it is verified,
// otherwise the account's other verified address that sorts first by
// address; "" if none is verified. Unlike PrimaryVerifiedEmail, a verified
// secondary counts: an account that verified one address but not its
// primary still has somewhere to send a login link.
func (s *Store) PreferredVerifiedEmail(userID int64) (string, error) {
	var addr string
	err := s.DB.QueryRow(
		`SELECT address FROM emails WHERE user_id = ? AND verified_at IS NOT NULL
		 ORDER BY is_primary DESC, address LIMIT 1`,
		userID).Scan(&addr)
	if errors.Is(err, sql.ErrNoRows) {
		return "", nil
	}
	return addr, err
}