import OrgSwift
import SwiftUI

/// Renders org-mode as native SwiftUI.
///
/// ```swift
/// OrgView(source, options: OrgRenderOptions(host: "gitbay.org", owner: "krz",
///                                           repositoryName: "org-swift"))
/// ```
///
/// The parse, footnote numbering, URL resolution and syntax highlighting run once off
/// `body`, in a task keyed to the source *and the color scheme*, so scrolling and Dynamic
/// Type changes do not re-derive them — but switching to dark mode does, because a
/// ``OrgCodeStyler`` bakes its theme's colors into the text it returns. Text is selectable,
/// links open through the environment's `openURL`, and everything scales with Dynamic Type.
public struct OrgView: View {
    private let source: String
    private let options: OrgRenderOptions
    private let styler: OrgCodeStyler
    private let keywords: OrgKeywordStyle
    private let textTransform: ((inout AttributedString) -> Void)?

    @Environment(\.colorScheme) private var colorScheme
    @State private var layout = OrgLayout()

    /// - Parameter textTransform: runs on each run of prose after styling: paragraphs,
    ///   headings, list terms, table cells, verse, captions and footnotes, never a code
    ///   block. Code and verbatim runs carry the `.code` inline presentation intent and
    ///   links carry `.link`, so a transform can leave them alone. It is not part of the
    ///   layout key; changing it alone does not re-render.
    public init(
        _ source: String,
        options: OrgRenderOptions = .init(),
        styler: OrgCodeStyler = PlainOrgCodeStyler(),
        keywords: OrgKeywordStyle = .init(),
        textTransform: ((inout AttributedString) -> Void)? = nil
    ) {
        self.source = source
        self.options = options
        self.styler = styler
        self.keywords = keywords
        self.textTransform = textTransform
    }

    public var body: some View {
        VStack(alignment: .leading, spacing: 12) {
            OrgBlockListView(blocks: layout.blocks)
            if !layout.footnotes.isEmpty {
                OrgFootnotesView(footnotes: layout.footnotes)
            }
        }
        .frame(maxWidth: .infinity, alignment: .leading)
        .textSelection(.enabled)
        .task(id: LayoutKey(source: source, colorScheme: colorScheme)) {
            layout = OrgLayoutBuilder(options: options, styler: styler, keywords: keywords,
                                      textTransform: textTransform)
                .layout(OrgParser.parse(source))
        }
    }
}

/// What the prepared layout depends on. Highlighted code carries baked-in colors, so the
/// scheme belongs in the key alongside the source.
private struct LayoutKey: Equatable {
    var source: String
    var colorScheme: ColorScheme
}

/// The notes section org's exporter puts at the end of a document.
struct OrgFootnotesView: View {
    let footnotes: [OrgFootnote]

    var body: some View {
        VStack(alignment: .leading, spacing: 6) {
            Divider()
            ForEach(footnotes) { note in
                HStack(alignment: .firstTextBaseline, spacing: 6) {
                    Text("\(note.number).")
                        .font(.footnote)
                        .monospacedDigit()
                        .foregroundStyle(.secondary)
                    Text(note.text)
                        .fixedSize(horizontal: false, vertical: true)
                        .frame(maxWidth: .infinity, alignment: .leading)
                }
            }
        }
        .padding(.top, 8)
        .accessibilityLabel("Footnotes")
    }
}