import ByreAPI
import SwiftUI

typealias Todo = Components.Schemas.Todo
typealias TodoItem = Components.Schemas.TodoItem

private let refreshKinds: Set<String> = ["task.merged", "project.created"]

struct ProjectView: View {
    @Environment(Store.self) private var store
    @Environment(Overlays.self) private var overlays
    @ViewState private var todos: [String: Result<Todo, ApiError>] = [:]
    @ViewState private var off: (() -> Void)?

    var body: some View {
        ScrollView {
            if let p = store.focusedProject() {
                ProjectBlock(project: p, todo: todos[p.id])
                    .padding(.horizontal, 16)
                    .padding(.top, 8)
                    .padding(.bottom, 16)
            } else {
                Muted(text: "No project selected.")
            }
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
        .onAppear {
            off = store.events.add { ev in
                if refreshKinds.contains(ev.kind), let projectId = ev.projectId {
                    load(projectId)
                }
            }
            refresh()
        }
        .onDisappear {
            off?()
            off = nil
        }
        .onChange(of: store.connected) {
            if store.connected {
                refresh()
            }
        }
        .onChange(of: store.projects.map(\.id)) {
            refresh()
        }
        .onChange(of: store.focusedProject()?.id) {
            if let p = store.focusedProject(), todos[p.id] == nil {
                load(p.id)
            }
        }
    }

    private func refresh() {
        if let p = store.focusedProject() {
            load(p.id)
        }
    }

    private func load(_ projectId: String) {
        Task {
            do {
                todos[projectId] = .success(try await store.api.client.getTodo(path: .init(projectId: projectId)).ok.body.json)
            } catch {
                todos[projectId] = .failure(ApiError(status: 0, message: "Couldn't read TODO.md: \(errorText(error))"))
            }
        }
    }
}

private struct ProjectBlock: View {
    let project: Project
    let todo: Result<Todo, ApiError>?
    @Environment(Store.self) private var store

    var body: some View {
        let active = (store.tasks[project.id] ?? []).filter { $0.status == .active }
        VStack(alignment: .leading, spacing: 0) {
            HStack(alignment: .firstTextBaseline, spacing: 6) {
                Text(project.name).font(Fonts.font(13, weight: 700))
                Text(project.defaultBranch).font(Fonts.font(11)).foregroundStyle(Palette.muted)
            }
            .padding(.top, 16)
            .padding(.bottom, 6)
            heading("Tasks")
            TaskRows(active: active)
            heading("TODO")
            TodoBlock(project: project, todo: todo, active: active)
        }
        .frame(maxWidth: .infinity, alignment: .leading)
    }

    private func heading(_ text: String) -> some View {
        Text(text)
            .font(Fonts.font(12, weight: 700))
            .padding(.top, 14)
            .padding(.bottom, 4)
    }
}

@MainActor
private func nested(_ store: Store, _ active: [ByreTask]) -> [(task: ByreTask, depth: Int)] {
    let ids = Set(active.map(\.id))
    var out: [(task: ByreTask, depth: Int)] = []
    func add(_ task: ByreTask, _ depth: Int) {
        out.append((task, depth))
        for child in store.byRank(active.filter({ $0.parentTaskId == task.id }).reversed()) {
            add(child, depth + 1)
        }
    }
    for task in store.byRank(active.filter { $0.parentTaskId == nil || !ids.contains($0.parentTaskId!) }) {
        add(task, 0)
    }
    return out
}

private struct TaskRows: View {
    let active: [ByreTask]
    @Environment(Store.self) private var store

    var body: some View {
        if active.isEmpty {
            Text("No active tasks.")
                .foregroundStyle(Palette.muted)
                .padding(.horizontal, 10)
                .padding(.vertical, 6)
        } else {
            VStack(alignment: .leading, spacing: 0) {
                ForEach(nested(store, active), id: \.task.id) { row in
                    TaskRow(task: row.task, depth: row.depth)
                }
            }
            .padding(.bottom, 8)
        }
    }
}

struct HoverRow<Content: View>: View {
    var selected = false
    var indent: CGFloat = 0
    let action: () -> Void
    @ViewBuilder let content: Content
    @ViewState private var hover = false

    var body: some View {
        Button(action: action) {
            HStack(spacing: 10) {
                content
            }
            .padding(.leading, max(0, 10 + indent))
            .padding(.trailing, 10)
            .padding(.vertical, 6)
            .frame(maxWidth: .infinity, alignment: .leading)
            .background(selected ? Palette.accentTint : hover ? Palette.surface : .clear, in: RoundedRectangle(cornerRadius: 6))
            .contentShape(Rectangle())
        }
        .buttonStyle(.plain)
        .onHover { hover = $0 }
    }
}

private struct TaskRow: View {
    let task: ByreTask
    let depth: Int
    @Environment(Store.self) private var store

    var body: some View {
        let ts = store.taskState(task)
        let color = taskPalette[task.color]
        let count = store.inbox.filter { $0.taskId == task.id }.count
        HoverRow(selected: task.id == store.selectedTaskId, indent: task.parentTaskId != nil ? 20 * CGFloat(depth - 1) : 0) {
            store.focusTask(task.id)
        } content: {
            if let parent = task.parentTaskId {
                Text("↳")
                    .foregroundStyle(Palette.muted)
                    .help("Subtask of \(store.findTask(parent)?.title ?? parent)")
            }
            StateMark(state: ts, color: color)
            Text(task.title)
                .foregroundStyle(color)
                .lineLimit(1)
                .truncationMode(.tail)
                .frame(maxWidth: .infinity, alignment: .leading)
            if count > 0 {
                Badge(count: count).help("open questions")
            }
            if ts.kind == .idle && store.unreadSummary(task) {
                Text("new summary")
                    .font(Fonts.font(11, weight: 700))
                    .foregroundStyle(Palette.accent)
                    .help("A turn summary you haven't read")
                    .accessibilityLabel("New summary from \(task.title), unread")
            } else {
                Text(ts.label)
                    .font(Fonts.font(11))
                    .foregroundStyle(ts.needsYou ? Palette.warn : Palette.muted)
                    .help(ts.title)
            }
        }
    }
}

private struct TodoBlock: View {
    let project: Project
    let todo: Result<Todo, ApiError>?
    let active: [ByreTask]

    var body: some View {
        switch todo {
        case .none:
            row("Loading…")
        case .failure(let e):
            row(e.message, error: true)
        case .success(let t):
            if !t.exists {
                row("No TODO.md on \(project.defaultBranch).")
            } else if t.items.isEmpty {
                row("TODO.md has no items.")
            } else {
                VStack(alignment: .leading, spacing: 0) {
                    ForEach(Array(t.items.enumerated()), id: \.offset) { i, item in
                        if !item.section.isEmpty && (i == 0 || t.items[i - 1].section != item.section) {
                            Text(item.section)
                                .font(Fonts.font(12, weight: 700))
                                .foregroundStyle(Palette.muted)
                                .padding(.top, i == 0 ? 10 : 2)
                                .padding(.bottom, 4)
                        }
                        TodoRow(project: project, item: item, task: active.first { $0.todoItem == item.title })
                            .padding(.bottom, i == t.items.count - 1 || t.items[i + 1].section != item.section ? 8 : 0)
                    }
                }
            }
        }
    }

    private func row(_ text: String, error: Bool = false) -> some View {
        Text(text)
            .foregroundStyle(error ? Palette.danger : Palette.muted)
            .padding(.horizontal, 10)
            .padding(.vertical, 6)
    }
}

private struct TodoRow: View {
    let project: Project
    let item: TodoItem
    let task: ByreTask?
    @Environment(Store.self) private var store
    @Environment(Overlays.self) private var overlays

    var body: some View {
        VStack(alignment: .leading, spacing: 4) {
            HStack(spacing: 10) {
                Text(item.title)
                    .foregroundStyle(task.map { taskPalette[$0.color] } ?? Palette.text)
                    .frame(maxWidth: .infinity, alignment: .leading)
                    .fixedSize(horizontal: false, vertical: true)
                action
            }
            if !item.body.isEmpty {
                MarkdownView(blocks: parseMarkdown(item.body), ctx: MDContext(color: Palette.muted))
            }
        }
        .padding(.horizontal, 10)
        .padding(.vertical, 6)
        .background(task != nil && task?.id == store.selectedTaskId ? Palette.accentTint : .clear, in: RoundedRectangle(cornerRadius: 6))
    }

    @ViewBuilder
    private var action: some View {
        if let task {
            let ts = store.taskState(task)
            Button {
                store.focusTask(task.id)
            } label: {
                HStack(spacing: 6) {
                    StateMark(state: ts, color: taskPalette[task.color])
                    Text(ts.label)
                }
                .font(Fonts.font(11))
                .foregroundStyle(Palette.muted)
                .contentShape(Rectangle())
            }
            .buttonStyle(.plain)
            .fixedSize()
        } else {
            let busy = store.todoStarting.contains("\(project.id)\n\(item.title)")
            HStack(spacing: 6) {
                Button(busy ? "Starting…" : "Start") {
                    store.startTodo(project.id, item.title, discuss: false, overlays)
                }
                .help("Start a task that gets straight to work")
                Button("Discuss") {
                    store.startTodo(project.id, item.title, discuss: true, overlays)
                }
                .help("Start a task that discusses it with you in chat before building anything")
            }
            .buttonStyle(WebButtonStyle())
            .disabled(busy)
            .fixedSize()
        }
    }
}