import { Injectable, computed, inject } from '@angular/core';
import {
  type Combo,
  EN_KEY_NAMES,
  effectiveKeymap,
  firesInTextField,
  formatCombo,
  isRepeatable,
  type KeyEventLike,
  type KeyNames,
  matchesEvent,
  parseCombo,
  type ResolvedBinding,
  type Scope,
  sameCombo,
  serializeCombo,
  type ShortcutId,
} from '@shared/keymap';
import { I18nService } from './i18n.service';
import { IS_MAC } from './platform';
import { SettingsService } from './settings.service';

export type { ShortcutId } from '@shared/keymap';

/** A keydown as resolve() reads it: the matching fields plus where it came from. */
type KeyInput = KeyEventLike & { target?: EventTarget | null; isComposing?: boolean; keyCode?: number };

/**
 * The keyboard layer over the shared keymap (src/shared/keymap.ts): resolves
 * keydowns against the EFFECTIVE keymap — defaults plus the Settings → Keyboard
 * remaps, live in every window — and formats the hints menus and tooltips show.
 *
 * - Matching is exact: ⌃F is not ⌘F, Ctrl+Tab is not Tab. `Mod` is ⌘ on
 *   macOS and Ctrl elsewhere.
 * - On macOS the PAGE sees ⌘-keys first: WKWebView hands key equivalents to the
 *   page before the app menu (WebKit's WebViewImpl::performKeyEquivalent), so a
 *   key a window claims here (claim() → preventDefault) never reaches the menu
 *   bar, whose accelerators bun builds from the same table. Keys nobody claims
 *   fall through to it.
 * - From a text field only firesInTextField() combos count (⌘S yes, Delete no).
 * - Escape, the arrows inside menus and dialog Enter stay component-local:
 *   they are fixed, so nobody can remap themselves out of a dialog.
 */
@Injectable({ providedIn: 'root' })
export class ShortcutsService {
  private readonly settings = inject(SettingsService);
  private readonly i18n = inject(I18nService);

  readonly keymap = computed(() => effectiveKeymap(this.settings.keybindings(), IS_MAC));
  private readonly byId = computed(() => new Map(this.keymap().map((b) => [b.id, b])));
  /** Localized key names for the non-mac spelling ("Strg+Entf"); reading t()
   *  makes every hint follow a language switch. */
  private readonly names = computed<KeyNames>(() => {
    const names = { ...EN_KEY_NAMES };
    for (const key of Object.keys(names) as (keyof KeyNames)[]) {
      names[key] = this.i18n.t(`keys.names.${key}`);
    }
    return names;
  });

  /** The command a keydown triggers in `scope`, or null. Window scopes include
   *  `any`; `panel` doesn't (the window root runs those). */
  resolve(event: KeyInput, scope: Scope): ShortcutId | null {
    // an IME's Enter commits a candidate, it is never a shortcut
    if (event.isComposing || event.keyCode === 229) return null;
    const typing = this.isTypingTarget(event);
    for (const binding of this.keymap()) {
      if (!binding.scopes.includes(scope) && (scope === 'panel' || !binding.scopes.includes('any'))) {
        continue;
      }
      for (const combo of binding.combos) {
        if (typing && !firesInTextField(combo, IS_MAC)) continue;
        if (matchesEvent(combo, event, IS_MAC)) return binding.id;
      }
    }
    return null;
  }

  /**
   * resolve() + take the key: a match is preventDefault-ed, so the macOS menu
   * never runs it a second time. A held key repeats only movement-like
   * commands; any other repeat is swallowed (holding ⌘W closes one tab).
   */
  claim(event: KeyboardEvent, scope: Scope): ShortcutId | null {
    const id = this.resolve(event, scope);
    if (!id) return null;
    event.preventDefault();
    return event.repeat && !isRepeatable(id) ? null : id;
  }

  /** Whether a keydown is one of `id`'s combos (an open menu matching its items). */
  matches(id: ShortcutId, event: KeyEventLike): boolean {
    return !!this.byId().get(id)?.combos.some((c) => matchesEvent(c, event, IS_MAC));
  }

  binding(id: ShortcutId): ResolvedBinding | undefined {
    return this.byId().get(id);
  }

  format(combo: Combo): string {
    return formatCombo(combo, IS_MAC, this.names());
  }

  /** The hint menus show: the command's first key, or '' when unbound. */
  label(id: ShortcutId): string {
    const first = this.byId().get(id)?.combos[0];
    return first ? this.format(first) : '';
  }

  labels(id: ShortcutId): string[] {
    return (this.byId().get(id)?.combos ?? []).map((c) => this.format(c));
  }

  /** A tooltip with the command's keys: "Delete (F8 / Del)"; bare when unbound. */
  tip(text: string, id: ShortcutId): string {
    const keys = this.labels(id);
    return keys.length ? `${text} (${keys.join(' / ')})` : text;
  }

  /** A FIXED key — one no remap moves, such as Enter in the find box — in
   *  the platform's spelling (⇧↩ / Shift+Enter). */
  fixedKey(combo: string): string {
    const parsed = parseCombo(combo, IS_MAC);
    return parsed ? this.format(parsed) : combo;
  }

  /** tip() for a fixed key. */
  tipFixed(text: string, combo: string): string {
    return `${text} (${this.fixedKey(combo)})`;
  }

  /**
   * Store new combos for commands (Settings → Keyboard). Only rows that differ
   * from their defaults are kept, so a reset — or a remap back to the
   * default — leaves nothing behind.
   */
  rebind(changes: Partial<Record<ShortcutId, Combo[]>>): void {
    const next = { ...this.settings.keybindings() };
    for (const [id, combos] of Object.entries(changes) as [ShortcutId, Combo[]][]) {
      const defaults = this.byId().get(id)?.defaults ?? [];
      const isDefault =
        combos.length === defaults.length && combos.every((c, i) => sameCombo(c, defaults[i]));
      if (isDefault) delete next[id];
      else next[id] = combos.map(serializeCombo);
    }
    this.settings.setKeybindings(next);
  }

  resetAll(): void {
    this.settings.setKeybindings({});
  }

  /** The platform command modifier: ⌘ on macOS, Ctrl elsewhere — exactly one.
   *  Mouse events too: Mod+click toggle-selects in the panels. */
  isMod(event: KeyboardEvent | MouseEvent): boolean {
    return IS_MAC ? event.metaKey : event.ctrlKey;
  }

  /** True when the event comes from something the user types into. */
  isTypingTarget(event: { target?: EventTarget | null }): boolean {
    const target = event.target as HTMLElement | null;
    return !!target?.closest?.(
      'textarea, select, [contenteditable="true"], input:not([type=checkbox]):not([type=radio]):not([type=button])',
    );
  }
}