import SwiftUI

/// Editor for per-playlist grouping template.
/// Lets the user type a custom template or pick a preset.
struct GroupTemplateEditorSheet: View {
    let playlist: Playlist
    @EnvironmentObject private var theme: AppTheme
    @Environment(\.modelContext) private var modelContext
    @Environment(\.dismiss) private var dismiss

    @State private var template: String = ""

    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            // Title
            HStack {
                Text("Track Grouping")
                    .font(.title3.bold())
                Spacer()
                Button("Cancel") { dismiss() }
                    .keyboardShortcut(.cancelAction)
                Button("Save") {
                    playlist.groupTemplate = template
                    try? modelContext.save()
                    dismiss()
                }
                .keyboardShortcut(.defaultAction)
            }

            // Template text field
            VStack(alignment: .leading, spacing: 4) {
                Text("Group Template")
                    .font(.caption.bold())
                    .foregroundStyle(.secondary)

                TextField("e.g. {Album} ({Year})", text: $template)
                    .font(.body.monospaced())
                    .textFieldStyle(.roundedBorder)

                Text("Use placeholders like {Album}, {Artist}, {Year}, etc. Tracks with the same resolved value will be grouped together. Empty = no grouping.")
                    .font(.caption)
                    .foregroundStyle(.secondary)
            }

            Divider()

            // Presets
            VStack(alignment: .leading, spacing: 6) {
                Text("Presets")
                    .font(.caption.bold())
                    .foregroundStyle(.secondary)

                LazyVGrid(columns: [GridItem(.adaptive(minimum: 140))], spacing: 4) {
                    ForEach(GroupTemplateResolver.presets, id: \.template) { preset in
                        Button {
                            template = preset.template
                        } label: {
                            HStack(spacing: 6) {
                                VStack(alignment: .leading, spacing: 1) {
                                    Text(preset.name)
                                        .font(.system(size: 12, weight: .medium))
                                    if !preset.template.isEmpty {
                                        Text(preset.template)
                                            .font(.system(size: 10, design: .monospaced))
                                            .foregroundStyle(.secondary)
                                    }
                                }
                                Spacer(minLength: 0)
                                if template == preset.template {
                                    Image(systemName: "checkmark")
                                        .foregroundStyle(.green)
                                        .font(.system(size: 11))
                                }
                            }
                            .padding(6)
                            .background(template == preset.template ? Color.accentColor.opacity(0.1) : Color.primary.opacity(0.03))
                            .clipShape(RoundedRectangle(cornerRadius: 6))
                            .overlay(
                                RoundedRectangle(cornerRadius: 6)
                                    .stroke(template == preset.template ? Color.accentColor : Color.gray.opacity(0.2), lineWidth: 1)
                            )
                        }
                        .buttonStyle(.plain)
                    }
                }
            }

            Divider()

            // Placeholders (tap to insert)
            VStack(alignment: .leading, spacing: 6) {
                Text("Placeholders (click to insert)")
                    .font(.caption.bold())
                    .foregroundStyle(.secondary)

                HStack(spacing: 6) {
                    ForEach(GroupTemplateResolver.placeholders, id: \.token) { placeholder in
                        Button {
                            template += placeholder.token
                        } label: {
                            Text(placeholder.token)
                                .font(.system(size: 11, design: .monospaced))
                                .padding(.horizontal, 6)
                                .padding(.vertical, 3)
                                .background(Color.accentColor.opacity(0.1))
                                .clipShape(RoundedRectangle(cornerRadius: 4))
                        }
                        .buttonStyle(.plain)
                        .help(placeholder.description)
                    }
                }
            }

            // Preview
            if !template.isEmpty {
                Divider()

                VStack(alignment: .leading, spacing: 4) {
                    Text("Preview")
                        .font(.caption.bold())
                        .foregroundStyle(.secondary)

                    Text(previewText)
                        .font(.system(size: 13, weight: .semibold))
                        .foregroundStyle(theme.primaryText)
                        .padding(8)
                        .frame(maxWidth: .infinity, alignment: .leading)
                        .background(Color.primary.opacity(0.04))
                        .clipShape(RoundedRectangle(cornerRadius: 6))
                }
            }

            Spacer()
        }
        .padding(20)
        .frame(width: 560, height: 440)
        .onAppear {
            template = playlist.groupTemplate
        }
    }

    private var previewText: String {
        let sample = template
            .replacingOccurrences(of: "{Artist}", with: "Raimundo Fagner")
            .replacingOccurrences(of: "{Album}", with: "Raimundo Fagner (1973)")
            .replacingOccurrences(of: "{Genre}", with: "MPB")
            .replacingOccurrences(of: "{Year}", with: "2026")
            .replacingOccurrences(of: "{Folder}", with: "Batch 1")
            .replacingOccurrences(of: "{Format}", with: "FLAC")
            .replacingOccurrences(of: "{BPM}", with: "90-100 BPM")
            .replacingOccurrences(of: "{Key}", with: "Am")
        return sample
    }
}