// Copyright (C) 2024 Rubén Beltrán del Río

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program. If not, see https://map.tranquil.systems.

import SwiftUI

struct TemplatesPreferencesView: View {
  @AppStorage("mapTemplates") private var templatesData: Data = UserPreferences.Defaults
    .mapTemplates
  @State private var selectedTemplate: Template?
  @State private var showingAddSheet = false
  @State private var newTemplateName = ""
  @State private var showingHelpPopover = false

  private var templates: Binding<[Template]> {
    Binding(
      get: {
        if let decoded = try? JSONDecoder().decode([Template].self, from: templatesData) {
          return decoded
        }
        return []
      },
      set: { newValue in
        if let encoded = try? JSONEncoder().encode(newValue) {
          templatesData = encoded
        }
      }
    )
  }

  private var selectedTemplateContent: Binding<String> {
    Binding(
      get: {
        guard let selected = selectedTemplate,
          let template = templates.wrappedValue.first(where: { $0.id == selected.id })
        else { return "" }
        return template.content
      },
      set: { newContent in
        guard let selected = selectedTemplate,
          let index = templates.wrappedValue.firstIndex(where: { $0.id == selected.id })
        else { return }

        var currentTemplates = templates.wrappedValue
        currentTemplates[index].content = newContent
        templates.wrappedValue = currentTemplates
      }
    )
  }

  var body: some View {
    VStack(alignment: .leading, spacing: Dimensions.Spacing.regular) {
      HStack(spacing: Dimensions.Spacing.cozy) {
        VStack(alignment: .leading, spacing: Dimensions.Spacing.regular) {
          List(templates.wrappedValue) { template in
            HStack(spacing: Dimensions.Spacing.coziest) {
              if selectedTemplate?.id == template.id {
                Button(action: { setDefaultTemplate(template) }) {
                  Image(systemName: template.isDefault ? "largecircle.fill.circle" : "circle")
                    .foregroundColor(Color.white)
                }
                .buttonStyle(.plain)
                .keyboardShortcut("d", modifiers: [.command])
                .help("preferences.templates.help.set_as_default")
              } else {
                Button(action: { setDefaultTemplate(template) }) {
                  Image(systemName: template.isDefault ? "largecircle.fill.circle" : "circle")
                    .foregroundColor(
                      template.isDefault
                        ? Color.Theme.UI.accent : Color.Theme.UI.foreground.opacity(0.5))
                }
                .buttonStyle(.plain)
                .help("preferences.templates.help.set_as_default")
              }

              Text(template.name)
                .font(.Theme.Body.regular)
                .kerning(Dimensions.Kerning.body)
                .tag(template)
                .foregroundColor(
                  selectedTemplate?.id == template.id ? Color.white : Color.Theme.UI.foreground
                )

              Spacer()
            }
            .padding(Dimensions.Spacing.cozy)
            .background(selectedTemplate?.id == template.id ? Color.Theme.UI.accent : Color.clear)
            .clipShape(RoundedRectangle(cornerRadius: Dimensions.Preferences.Sidebar.radius))
            .padding(Dimensions.Spacing.coziest)
            .listRowInsets(EdgeInsets())
            .listRowSeparator(.hidden)
            .onTapGesture {
              selectedTemplate = template
            }
          }
          .listStyle(.plain)
          .border(Color.Theme.UI.foreground.opacity(0.2), width: 1)

          HStack(spacing: Dimensions.Spacing.regular) {

            Spacer()

            Button(action: { showingHelpPopover = true }) {
              Image(systemName: "questionmark.circle")
            }
            .buttonStyle(.borderless)
            .popover(isPresented: $showingHelpPopover, arrowEdge: .bottom) {
              Text("preferences.templates.explanation")
                .font(.Theme.Body.regular)
                .kerning(Dimensions.Kerning.body)
                .lineSpacing(Dimensions.LineHeight.body - Dimensions.FontSize.body)
                .frame(width: 300)
                .padding(Dimensions.Spacing.regular)
            }

            HStack(spacing: Dimensions.Spacing.coziest) {
              Button(action: { showingAddSheet = true }) {
                Image(systemName: "plus")
              }
              .keyboardShortcut("t", modifiers: [.command])
              .help("preferences.templates.help.add")

              Button(action: {
                removeTemplate(selectedTemplate)
              }) {
                Image(systemName: "minus")
              }
              .keyboardShortcut(.delete, modifiers: [.command])
              .help("preferences.templates.help.remove \(selectedTemplate?.name ?? "")")
              .disabled(selectedTemplate == nil)
            }
          }
        }
        .frame(width: Dimensions.Preferences.Sidebar.width)

        Divider()

        VStack(alignment: .leading, spacing: Dimensions.Spacing.regular) {
          if selectedTemplate != nil {
            MapTextEditor(text: selectedTemplateContent)
              .border(Color.Theme.UI.foreground.opacity(0.2), width: 1)
          } else {
            VStack {
              Spacer()
              Text("preferences.templates.empty_view")
                .foregroundColor(.secondary)
              Spacer()
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
          }
        }
        .frame(maxWidth: .infinity, maxHeight: .infinity)
      }
      .onAppear {
        // Set first template as selected if none is selected
        if selectedTemplate == nil && !templates.wrappedValue.isEmpty {
          selectedTemplate = templates.wrappedValue.first
        }
      }
      .sheet(isPresented: $showingAddSheet) {
        VStack(spacing: Dimensions.Spacing.indulgent) {
          Text("preferences.templates.new_template.title")
            .font(.Theme.Body.emphasized)
            .kerning(Dimensions.Kerning.body)

          TextField("preferences.templates.new_template.placeholder", text: $newTemplateName)
            .textFieldStyle(.roundedBorder)
            .font(.Theme.Body.regular)
            .kerning(Dimensions.Kerning.body)
            .onSubmit {
              addTemplate()
            }

          HStack(spacing: Dimensions.Spacing.coziest) {

            Spacer()
            Button(
              action: {
                showingAddSheet = false
                newTemplateName = ""
              },
              label: {
                Text("preferences.templates.new_template.cancel")
                  .font(.Theme.Body.regular)
                  .kerning(Dimensions.Kerning.body)
              }
            )
            .keyboardShortcut(.escape)
            Button(
              action: {
                addTemplate()
              },
              label: {
                Text("preferences.templates.new_template.add")
                  .font(.Theme.Body.regular)
                  .kerning(Dimensions.Kerning.body)
              }
            )
            .keyboardShortcut(.return)
            .disabled(newTemplateName.isEmpty)
          }
        }
        .padding(Dimensions.Spacing.loose)
        .frame(width: 300, height: 120)
      }
    }.padding(.vertical, Dimensions.Spacing.loose)
      .padding(.horizontal, Dimensions.Spacing.indulgent)
  }

  private func addTemplate() {
    let newTemplate = Template(
      name: newTemplateName.isEmpty
        ? String(localized: "map_template.empty.title") : newTemplateName,
      content: ""
    )
    var currentTemplates = templates.wrappedValue
    currentTemplates.append(newTemplate)
    templates.wrappedValue = currentTemplates
    selectedTemplate = newTemplate
    showingAddSheet = false
    newTemplateName = ""
  }

  private func removeTemplate(_ template: Template?) {
    guard let template else { return }
    var currentTemplates = templates.wrappedValue
    currentTemplates.removeAll { $0 == template }
    templates.wrappedValue = currentTemplates
    selectedTemplate = templates.wrappedValue.first
  }

  private func setDefaultTemplate(_ template: Template) {
    // Direct assignment to binding - this will automatically save via @AppStorage
    templates.wrappedValue = templates.wrappedValue.map { t in
      var newTemplate = t
      newTemplate.isDefault = (t.id == template.id)
      return newTemplate
    }
  }
}

#Preview {
  TemplatesPreferencesView()
}