import OrgSwift
import SwiftUI

/// A list, recursing into its own sublists.
///
/// SwiftUI has no list-layout primitive, so the marker sits in its own column and the content
/// hangs beside it — wrapped lines line up under the text, not under the bullet.
struct OrgListView: View {
    let list: OrgListLayout
    /// Ordered numbering restarts at each nesting level, as in org.
    var body: some View {
        VStack(alignment: .leading, spacing: 6) {
            ForEach(Array(list.items.enumerated()), id: \.element.id) { index, item in
                if list.kind == .description {
                    descriptionItem(item)
                } else {
                    markedItem(item, marker: marker(at: index))
                }
            }
        }
    }

    private func marker(at index: Int) -> String {
        list.kind == .ordered ? "\(index + 1)." : "•"
    }

    private func markedItem(_ item: OrgListLayout.Item, marker: String) -> some View {
        HStack(alignment: .firstTextBaseline, spacing: 8) {
            Text(marker)
                .monospacedDigit()
                .foregroundStyle(.secondary)
            VStack(alignment: .leading, spacing: 6) {
                if let checkbox = item.checkbox {
                    HStack(alignment: .firstTextBaseline, spacing: 6) {
                        Image(systemName: Self.symbol(for: checkbox))
                            .foregroundStyle(checkbox == .on ? Color.accentColor : .secondary)
                            .accessibilityLabel(Self.label(for: checkbox))
                        paragraphs(item)
                    }
                } else {
                    paragraphs(item)
                }
                if let sublist = item.sublist {
                    OrgListView(list: sublist)
                }
            }
        }
    }

    /// `term :: definition` — the term above, the definition indented under it.
    private func descriptionItem(_ item: OrgListLayout.Item) -> some View {
        VStack(alignment: .leading, spacing: 2) {
            if let term = item.term {
                Text(term).fixedSize(horizontal: false, vertical: true)
            }
            paragraphs(item).padding(.leading, 16)
            if let sublist = item.sublist {
                OrgListView(list: sublist).padding(.leading, 16)
            }
        }
    }

    private func paragraphs(_ item: OrgListLayout.Item) -> some View {
        VStack(alignment: .leading, spacing: 6) {
            ForEach(Array(item.paragraphs.enumerated()), id: \.offset) { _, paragraph in
                Text(paragraph)
                    .fixedSize(horizontal: false, vertical: true)
                    .frame(maxWidth: .infinity, alignment: .leading)
            }
        }
    }

    private static func symbol(for checkbox: OrgCheckbox) -> String {
        switch checkbox {
        case .on: "checkmark.square.fill"
        case .off: "square"
        case .partial: "minus.square"
        }
    }

    private static func label(for checkbox: OrgCheckbox) -> String {
        switch checkbox {
        case .on: "Done"
        case .off: "Not done"
        case .partial: "Partly done"
        }
    }
}