lanework/Kanban/UI/StyleEditor.swift

import AppKit
import SwiftUI

/// **The one style editor** — "a background palette grid and a curated symbol grid — presented from
/// three anchors" (03-board-ui.md § Styling ▸ Controls), plus the two small surfaces that stand
/// beside it: the quick-style recents row the context menus carry, and the funnel every anchor's
/// writes pass through.
///
/// This file is deliberately anchor-agnostic. It knows a `BoardStore`, a `StyleTarget` and the app's
/// recents, and nothing at all about popovers, card-window sidebars or the board popover — which is
/// what lets "one component, one behavior, three anchors" be a fact about the code rather than a
/// promise. The Style… popover's *lifecycle* lives elsewhere for the same reason: it is a reload
/// rule, and it belongs with the other reload rules (`StyleEditorSession`, `TransientBoardState`).

// MARK: - The write funnel

/// Where every style application from every anchor goes: the store's write, and the recents list
/// that the write feeds.
///
/// **It exists so "updated on every background application from any anchor" is structural.** Two
/// surfaces apply backgrounds — the editor's wells and the quick-style row — and the recents list is
/// app-wide state a board store has no business knowing about (02-architecture.md § Per-board app
/// state), so neither of them may be trusted to remember it and neither may be given the job alone.
///
/// **The None well never records.** It is a *removal* — `background` leaves the file — so there is no
/// colour to remember; only `.set` reaches `StyleRecents.record`.
@MainActor
enum StyleCommand {
    static func apply(
        background: StyleChange = .keep,
        icon: StyleChange = .keep,
        to target: StyleTarget,
        in store: BoardStore,
        recents: StyleRecents
    ) {
        store.applyStyle(to: target, background: background, icon: icon)
        if case let .set(value) = background {
            recents.record(value)
        }
    }
}

// MARK: - The curated symbol set

/// The symbol grid's contents — "a hand-picked set (roughly five dozen kanban-relevant SF Symbols)"
/// (03-board-ui.md § Styling ▸ Controls).
///
/// The pathfinder's two quick-pick lists (card markers, container-like stages) and its browser
/// fallback set are the seed, widened to one grid's worth: the rewrite has no full-catalog browser
/// to fall back to — "no full-browser escape hatch in-app; the raw file is the escape hatch" — so
/// this set has to stand alone for the common case, and it is grouped by what a board item *is*
/// rather than alphabetically so scanning it works.
///
/// **Filtered through `ItemSymbol.exists` at read time**, for the same reason the renderer is
/// lenient: symbol inventories grow per macOS release, and a name this OS does not know would draw
/// an empty well. A curated list is a convenience, never a claim about the running system.
enum CuratedSymbols {

    /// Every well in the grid, in order. Deliberately a stored constant rather than a computed
    /// property: the list is the design decision, and `available` is the only thing the OS gets a
    /// say in.
    static let all: [String] = [
        // Status and flow
        "flag", "flag.checkered", "star", "bolt", "checkmark.circle", "checkmark.seal",
        "xmark.circle", "exclamationmark.triangle", "questionmark.circle", "circle",
        "pause.circle", "play.circle",
        // Time
        "hourglass", "clock", "alarm", "calendar", "timer",
        // Work and craft
        "hammer", "wrench.and.screwdriver", "gearshape", "ant", "lightbulb", "paintbrush", "pencil",
        // Documents
        "doc.text", "doc.on.doc", "note.text", "list.bullet", "list.bullet.rectangle",
        "checklist", "book", "bookmark",
        // Containers and stages
        "tray", "tray.full", "folder", "archivebox", "shippingbox", "square.stack",
        // People and communication
        "person", "person.2", "bubble.left", "bubble.left.and.bubble.right", "envelope", "megaphone",
        // Data and systems
        "chart.bar", "chart.pie", "chart.line.uptrend.xyaxis", "terminal", "network",
        // Markers
        "tag", "paperclip", "link", "pin", "target", "flame", "leaf", "sparkles", "heart",
        // Motion
        "arrow.triangle.branch", "arrow.triangle.2.circlepath", "arrow.up.arrow.down",
        // Other
        "lock", "key", "trash",
    ]

    /// The set this Mac can actually draw.
    static var available: [String] { all.filter(ItemSymbol.exists) }
}

// MARK: - The editor

/// The style editor: a background section and a symbol section, each a leading "no value" well
/// followed by its grid, with the target set's current value stated beside the section title.
///
/// ### What it shows for a batch
///
/// Per dimension, `StyleFieldState`: every target agreeing shows that well selected, a disagreement
/// shows nothing selected and reads "—" ("Mixed" to VoiceOver — 10-accessibility.md's
/// never-colour-alone rule), and an off-palette value — a hand-written hex, an uncurated symbol —
/// states itself verbatim beside the title, outside the grids, where "choosing any well replaces
/// it".
///
/// ### Keyboard
///
/// "Inside the editor the grids are arrow-navigable and every well Tab-reachable" (§ Controls,
/// 10-accessibility.md): every well is a focusable button, and each grid moves focus by one on
/// ←/→ and by a row on ↑/↓.
struct StyleEditorView: View {

    let store: BoardStore
    let recents: StyleRecents
    let target: StyleTarget

    /// Wells per row. Thirteen background wells (None + the twelve) fall as 7 + 6, which keeps the
    /// popover narrow enough to sit beside a card without covering the lane it came from.
    private let backgroundColumns = 7
    private let symbolColumns = 8

    var body: some View {
        let subjects = store.styleSubjects(of: target)
        let background = StyleFieldState.resolve(subjects.map(\.background))
        let icon = StyleFieldState.resolve(subjects.map(\.icon))

        VStack(alignment: .leading, spacing: 14) {
            targetCaption(count: subjects.count)
            backgroundSection(background)
            Divider()
            symbolSection(icon)
        }
        .padding(14)
        .frame(width: 268)
        // The read-only lock and the focused-editor rule disable every mutating surface, not only
        // the menu items (02-architecture.md § The lock's scope) — an editor whose wells would be
        // refused should not look available. The popover stays *open*: the lock is a condition the
        // banner is already explaining, not a reason to yank a surface out from under the pointer.
        .disabled(!store.acceptsBoardMutations)
    }

    /// Who is being styled — one quiet line, because a batch gesture with no statement of its scope
    /// is the one place this editor could silently do more than the user meant.
    private func targetCaption(count: Int) -> some View {
        Text(caption(count: count))
            .font(.caption)
            .foregroundStyle(.secondary)
    }

    private func caption(count: Int) -> String {
        switch store.styleLevel(of: target) {
        case .board: "Board"
        case .lane: count == 1 ? "Lane" : "\(count) lanes"
        case .card: count == 1 ? "Card" : "\(count) cards"
        }
    }

    // MARK: - Background

    /// The twelve palette wells and their leading None (03-board-ui.md § Styling ▸ Controls:
    /// "palette-only in-app … plus a leading **None** well that removes the `background` key").
    private func backgroundSection(_ state: StyleFieldState) -> some View {
        VStack(alignment: .leading, spacing: 8) {
            sectionHeader("Background", current: backgroundCurrent(state))
            StyleWellGrid(
                wells: backgroundWells(state),
                columns: backgroundColumns,
                apply: { change in
                    StyleCommand.apply(background: change, to: target, in: store, recents: recents)
                }
            )
        }
    }

    private func backgroundWells(_ state: StyleFieldState) -> [StyleWell] {
        var wells = [StyleWell(id: 0, face: .noValue, label: "None", change: .remove, isSelected: state == .unset)]
        for (index, color) in Palette.backgrounds.enumerated() {
            wells.append(StyleWell(
                id: index + 1,
                face: .color(color.name),
                label: color.name,
                change: .set(color.name),
                isSelected: state == .uniform(color.name)
            ))
        }
        return wells
    }

    /// What the background dimension currently reads — including the verbatim off-palette case, which
    /// is exactly why this is a chip beside the title and not a highlighted well.
    private func backgroundCurrent(_ state: StyleFieldState) -> CurrentValue {
        switch state {
        case .unset: CurrentValue(face: .noValue, text: "None")
        case .mixed: CurrentValue(face: nil, text: "—", spoken: "Mixed")
        case let .uniform(value): CurrentValue(face: .color(value), text: value)
        }
    }

    // MARK: - Symbol

    /// The curated grid and its leading default well — "its leading well is the level's default
    /// symbol and removes the `icon` key" (§ Controls).
    private func symbolSection(_ state: StyleFieldState) -> some View {
        let level = store.styleLevel(of: target)
        let fallback = ItemSymbol.default(for: level)
        return VStack(alignment: .leading, spacing: 8) {
            sectionHeader("Symbol", current: symbolCurrent(state, fallback: fallback))
            ScrollView(.vertical) {
                StyleWellGrid(
                    wells: symbolWells(state, fallback: fallback),
                    columns: symbolColumns,
                    apply: { change in
                        StyleCommand.apply(icon: change, to: target, in: store, recents: recents)
                    }
                )
            }
            // Eight rows or so before it scrolls: enough that the grid reads as a set rather than as
            // a strip, short enough that the popover fits beside a card on a laptop screen.
            .frame(maxHeight: 168)
        }
    }

    private func symbolWells(_ state: StyleFieldState, fallback: String) -> [StyleWell] {
        var wells = [StyleWell(
            id: 0,
            face: .defaultSymbol(fallback),
            label: "Default (\(fallback))",
            change: .remove,
            isSelected: state == .unset
        )]
        for (index, name) in CuratedSymbols.available.enumerated() {
            wells.append(StyleWell(
                id: index + 1,
                face: .symbol(name),
                label: name,
                change: .set(name),
                isSelected: state == .uniform(name)
            ))
        }
        return wells
    }

    private func symbolCurrent(_ state: StyleFieldState, fallback: String) -> CurrentValue {
        switch state {
        case .unset: CurrentValue(face: .defaultSymbol(fallback), text: "Default")
        case .mixed: CurrentValue(face: nil, text: "—", spoken: "Mixed")
        case let .uniform(value): CurrentValue(face: .symbol(value), text: value)
        }
    }

    // MARK: - Section chrome

    private func sectionHeader(_ title: String, current: CurrentValue) -> some View {
        HStack(spacing: 6) {
            Text(title)
                .font(.subheadline.weight(.semibold))
            Spacer(minLength: 8)
            if let face = current.face {
                StyleWellFace(face: face, size: 14)
            }
            Text(current.text)
                .font(.caption)
                .foregroundStyle(.secondary)
                .lineLimit(1)
                .truncationMode(.middle)
        }
        .accessibilityElement(children: .ignore)
        .accessibilityLabel("\(title), \(current.spoken ?? current.text)")
    }
}

// MARK: - Current value

/// The current-value chip beside a section title: the one place an off-palette value is stated
/// ("labeled verbatim, outside the grids"), and the one place a mixed batch reads "—".
private struct CurrentValue {
    let face: StyleWellFace.Face?
    let text: String
    /// What VoiceOver says when the written text would not do — "Mixed" for the em dash, which is a
    /// glyph rather than a word (10-accessibility.md: a batch's mixed state "reads as 'mixed', never
    /// conveyed by highlight alone").
    var spoken: String?

    init(face: StyleWellFace.Face?, text: String, spoken: String? = nil) {
        self.face = face
        self.text = text
        self.spoken = spoken
    }
}

// MARK: - Wells

/// One well: what it draws, what it is called, and what clicking it asks of the frontmatter key.
private struct StyleWell: Identifiable {
    let id: Int
    let face: StyleWellFace.Face
    let label: String
    let change: StyleChange
    let isSelected: Bool
}

/// A well's face — a colour, a symbol, or one of the two "no value" leading wells.
private struct StyleWellFace: View {

    enum Face: Equatable {
        /// The background grid's None well: a slashed empty swatch, Finder's own vocabulary for
        /// "there isn't one".
        case noValue
        /// A palette name or a hand-written hex. An unresolvable value draws like `noValue` — the
        /// renderer's lenient rule, which is what makes an off-palette chip honest about a value the
        /// app cannot read.
        case color(String)
        case symbol(String)
        /// The symbol grid's leading well: the level's default, drawn quieter than a chosen one so
        /// "no symbol set" and "this symbol set" do not look alike.
        case defaultSymbol(String)
    }

    let face: Face
    var size: CGFloat = 20

    var body: some View {
        switch face {
        case .noValue:
            swatch(nil)
        case let .color(value):
            swatch(Palette.color(named: value))
        case let .symbol(name):
            glyph(name, tint: AnyShapeStyle(.primary))
        case let .defaultSymbol(name):
            glyph(name, tint: AnyShapeStyle(.secondary))
        }
    }

    /// A colour well. **Always stroked**: `chalk` is `#FFFFFF` and an unbordered white swatch is an
    /// invisible control on a light popover (10-accessibility.md's contrast stance turned on the
    /// app's own chrome). A `nil` colour adds the diagonal strike that means "none".
    private func swatch(_ color: Color?) -> some View {
        RoundedRectangle(cornerRadius: 4)
            .fill(color ?? Color(nsColor: .textBackgroundColor))
            .overlay { if color == nil { NoValueStrike().stroke(.secondary, lineWidth: 1) } }
            .overlay(RoundedRectangle(cornerRadius: 4).strokeBorder(.separator, lineWidth: 1))
            .frame(width: size, height: size)
    }

    private func glyph(_ name: String, tint: AnyShapeStyle) -> some View {
        Image(systemName: ItemSymbol.exists(name) ? name : "questionmark.square.dashed")
            .imageScale(.medium)
            .foregroundStyle(tint)
            .frame(width: size, height: size)
    }
}

/// The corner-to-corner slash on the None well — the pathfinder's swatch vocabulary, kept because it
/// is also the system's (an empty colour well slashes in Finder's own tag editor).
private struct NoValueStrike: Shape {
    func path(in rect: CGRect) -> Path {
        var path = Path()
        path.move(to: CGPoint(x: rect.minX + 3, y: rect.maxY - 3))
        path.addLine(to: CGPoint(x: rect.maxX - 3, y: rect.minY + 3))
        return path
    }
}

/// One grid of wells: Tab-reachable buttons, arrow-navigable as a grid (10-accessibility.md ▸ Style
/// editor).
///
/// Focus is the grid's own state rather than the editor's, because the two grids are independently
/// navigable and Tab is what crosses between them — which is exactly what the accessibility doc asks
/// for ("the grids are arrow-navigable and every well Tab-reachable"). The arrow handler sits on the
/// container: a focused `Button` does not consume arrow keys, so the press bubbles here, and moving
/// focus is all it does — **selection is never implied by focus**, since a well's job is to write to
/// disk and a stray arrow key must not restyle a board.
private struct StyleWellGrid: View {

    let wells: [StyleWell]
    let columns: Int
    let apply: (StyleChange) -> Void

    @FocusState private var focused: Int?

    var body: some View {
        LazyVGrid(
            columns: Array(repeating: GridItem(.flexible(minimum: 20), spacing: 6), count: columns),
            spacing: 6
        ) {
            ForEach(wells) { well in
                Button {
                    apply(well.change)
                } label: {
                    StyleWellFace(face: well.face)
                        .overlay(selectionRing(well.isSelected))
                        .contentShape(Rectangle())
                }
                .buttonStyle(.plain)
                .focusable()
                .focused($focused, equals: well.id)
                .help(well.label)
                .accessibilityLabel(well.label)
                .accessibilityAddTraits(well.isSelected ? [.isSelected] : [])
            }
        }
        .onKeyPress(keys: [.leftArrow, .rightArrow, .upArrow, .downArrow], phases: .down) { press in
            move(press.key)
        }
    }

    private func selectionRing(_ isSelected: Bool) -> some View {
        RoundedRectangle(cornerRadius: 5)
            .strokeBorder(isSelected ? AnyShapeStyle(Color.accentColor) : AnyShapeStyle(.clear), lineWidth: 2)
            .padding(-2)
    }

    /// One step per press, clamped at the ends rather than wrapped: a grid whose last row is short
    /// would wrap into a hole, and Finder's own icon grids clamp too.
    private func move(_ key: KeyEquivalent) -> KeyPress.Result {
        let delta: Int
        switch key {
        case .leftArrow: delta = -1
        case .rightArrow: delta = 1
        case .upArrow: delta = -columns
        case .downArrow: delta = columns
        default: return .ignored
        }
        let current = focused ?? 0
        let next = min(max(0, current + delta), wells.count - 1)
        focused = next
        return .handled
    }
}

// MARK: - Context-menu surfaces

/// The two style entries every context menu carries — Style… and the quick-style recents row
/// (11-command-nexus.md ▸ Context menus; 03-board-ui.md § Styling ▸ Controls).
///
/// One view for both menus because the entries are identical on a card and on a lane: only the
/// *target* differs, and that is the caller's to compute (the clicked item, or the selection it
/// belongs to).
struct StyleMenuItems: View {

    let store: BoardStore
    let recents: StyleRecents
    let target: StyleTarget

    var body: some View {
        Button("Style…") {
            store.transient.beginStyleEditor(for: target)
        }
        .disabled(!store.acceptsBoardMutations)

        QuickStyleRow(store: store, recents: recents, target: target)
    }
}

/// The quick-style row: "one compact row of recently used backgrounds … one-click recolor for the
/// common case; the pathfinder's second full-palette tier is gone" (03-board-ui.md § Styling ▸
/// Controls).
///
/// A `.palette`-styled `Picker` is what macOS renders as a horizontal swatch strip inside a menu —
/// the pathfinder's finding, and the only shape that puts colours in a menu row at all. AppKit draws
/// a menu item from an image and a title, so the dots are `NSImage`s (`PaletteSwatch`) rather than
/// SwiftUI shapes.
///
/// **Absent until it has something to offer.** A brand-new install has no recents, and an empty
/// picker in a context menu is a row that looks broken.
struct QuickStyleRow: View {

    let store: BoardStore
    let recents: StyleRecents
    let target: StyleTarget

    /// A sentinel for "the current value is not one of these", so a mixed batch — or a background
    /// that has aged out of the recents — leaves the row unchecked rather than checking the wrong
    /// dot. It is never a rendered option, so it can never be picked.
    private enum Choice: Hashable {
        case value(String)
        case other
    }

    var body: some View {
        if !recents.backgrounds.isEmpty {
            Picker("Recent Colors", selection: selection) {
                ForEach(recents.backgrounds, id: \.self) { name in
                    Label {
                        Text(name)
                    } icon: {
                        Image(nsImage: PaletteSwatch.circleImage(for: name))
                    }
                    .tag(Choice.value(name))
                }
            }
            .pickerStyle(.palette)
            .disabled(!store.acceptsBoardMutations)
        }
    }

    private var selection: Binding<Choice> {
        Binding(
            get: {
                let state = StyleFieldState.resolve(store.styleSubjects(of: target).map(\.background))
                guard case let .uniform(value) = state, recents.backgrounds.contains(value) else { return .other }
                return .value(value)
            },
            set: { picked in
                guard case let .value(name) = picked else { return }
                StyleCommand.apply(background: .set(name), to: target, in: store, recents: recents)
            }
        )
    }
}

// MARK: - Presentation

/// The Style… popover's content: the editor, aimed at **the session's own target set**.
///
/// Reading the target from the session rather than re-deriving it from the selection is what makes
/// the settled lifecycle visible: the popover was aimed once, at what the gesture named, and from
/// then on it follows *that* set as members vanish — a selection change behind an open popover must
/// not silently re-aim it, and a right-click on an unselected card must keep styling that card.
struct StyleEditorPopover: View {

    let store: BoardStore
    let recents: StyleRecents

    var body: some View {
        // Empty for the frame between a session ending and the popover's own dismissal landing —
        // the binding is already `false`, so this is a formality rather than a state.
        if let session = store.transient.styleEditor {
            StyleEditorView(store: store, recents: recents, target: session.target)
        }
    }
}

/// Whether *this* anchor is the one showing the open Style… popover.
///
/// Every candidate surface — a card face, a lane header, the strip itself — binds its popover
/// through this, and `StyleEditorSession.presentationAnchor(in:)` answers for exactly one of them.
/// So the popover follows its target set across reloads (an anchor that vanishes hands it to the next
/// live target) and only an *emptied* set takes it down, which is the settled lifecycle.
///
/// The setter is narrowed to this anchor's own dismissal: a session that has moved to another anchor
/// must not be discarded by the surface it just left.
@MainActor
func styleEditorPresentation(_ store: BoardStore, anchor: ItemID?) -> Binding<Bool> {
    Binding(
        // Spelled with an explicit `guard let` rather than optional chaining: `nil == nil` is
        // `true`, so a chained comparison would tell the board strip (whose anchor *is* `nil`) to
        // present a popover nobody opened.
        get: {
            guard let session = store.transient.styleEditor else { return false }
            return session.presentationAnchor(in: store.snapshot) == anchor
        },
        set: { presented in
            guard !presented,
                  let session = store.transient.styleEditor,
                  session.presentationAnchor(in: store.snapshot) == anchor
            else { return }
            store.transient.discardStyleEditor()
        }
    )
}