import SwiftUI

/// Editor for 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 {
        NavigationStack {
            List {
                Section {
                    TextField("Template (empty = no grouping)", text: $template)
                        .font(.body.monospaced())
                        .autocorrectionDisabled()
                        .textInputAutocapitalization(.never)
                } header: {
                    Text("Group Template")
                } footer: {
                    Text("Use placeholders like {Album}, {Artist}, {Date}, etc. You can also use {Year} as an alias for {Date}. Tracks with the same resolved value will be grouped together.")
                }

                Section("Presets") {
                    ForEach(GroupTemplateResolver.presets, id: \.template) { preset in
                        Button {
                            template = preset.template
                        } label: {
                            HStack {
                                VStack(alignment: .leading, spacing: 2) {
                                    Text(preset.name)
                                        .foregroundStyle(theme.primaryText)
                                    if !preset.template.isEmpty {
                                        Text(preset.template)
                                            .font(.caption.monospaced())
                                            .foregroundStyle(theme.tertiaryText)
                                    }
                                }
                                Spacer()
                                if template == preset.template {
                                    Image(systemName: "checkmark")
                                        .foregroundStyle(theme.accent)
                                }
                            }
                        }
                    }
                }

                Section("Available Placeholders") {
                    ForEach(GroupTemplateResolver.placeholders, id: \.token) { placeholder in
                        Button {
                            template += placeholder.token
                        } label: {
                            HStack {
                                Text(placeholder.token)
                                    .font(.body.monospaced())
                                    .foregroundStyle(theme.accent)
                                Spacer()
                                Text(placeholder.description)
                                    .font(.caption)
                                    .foregroundStyle(theme.tertiaryText)
                            }
                        }
                    }
                }

                if !template.isEmpty {
                    Section("Preview") {
                        Text("Groups will look like:")
                            .font(.caption)
                            .foregroundStyle(theme.tertiaryText)
                        Text(previewText)
                            .font(.subheadline.weight(.semibold))
                            .foregroundStyle(theme.groupHeaderText)
                    }
                }
            }
            .navigationTitle("Grouping")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("Cancel") { dismiss() }
                }
                ToolbarItem(placement: .confirmationAction) {
                    Button("Save") {
                        playlist.groupTemplate = template
                        try? modelContext.save()
                        dismiss()
                    }
                }
            }
            .onAppear {
                template = playlist.groupTemplate
            }
        }
    }

    private var previewText: String {
        // Show a sample with dummy data
        let sample = template
            .replacingOccurrences(of: "{Artist}", with: "Raekwon")
            .replacingOccurrences(of: "{Album}", with: "Only Built 4 Cuban Linx")
            .replacingOccurrences(of: "{Genre}", with: "Hip Hop")
            .replacingOccurrences(of: "{Date}", with: "1995")
            .replacingOccurrences(of: "{Year}", with: "1995")
            .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
    }
}