/**
 * History store backed by SQLite via Tauri commands.
 * Replaces the localStorage-based history management in page.svelte.js.
 *
 * All mutations call the backend first, then update the reactive state
 * on success. FTS5 search is handled server-side.
 */
import { invoke } from '@tauri-apps/api/core';

// Reactive state
let transcripts = $state([]);
let loading = $state(false);
let searchActive = $state(false);

// BroadcastChannel for multi-window sync
const historyChannel = typeof BroadcastChannel !== 'undefined'
  ? new BroadcastChannel('kon_history_v2')
  : null;

if (historyChannel) {
  historyChannel.onmessage = (event) => {
    if (event.data.type === 'history_updated') {
      transcripts.length = 0;
      transcripts.push(...event.data.transcripts);
    }
  };
}

function broadcastHistory() {
  if (historyChannel) {
    historyChannel.postMessage({
      type: 'history_updated',
      transcripts: $state.snapshot(transcripts),
    });
  }
}

/**
 * Load transcription history from the SQLite backend.
 * @param {number} [limit=100] - Maximum number of results
 */
export async function loadHistory(limit = 100) {
  loading = true;
  searchActive = false;
  try {
    const result = await invoke('list_all_transcripts', { limit });
    transcripts.length = 0;
    transcripts.push(...result);
  } catch (e) {
    console.error('Failed to load history:', e);
  } finally {
    loading = false;
  }
}

/**
 * Save a completed transcription to the SQLite backend.
 * Also saves segments if provided.
 *
 * @param {object} entry - Transcript data matching the save_transcript command params
 * @returns {Promise<boolean>} Whether the save succeeded
 */
export async function saveTranscript(entry) {
  try {
    await invoke('save_transcript', {
      id: entry.id,
      text: entry.text || '',
      source: entry.source || 'microphone',
      title: entry.title || null,
      audioPath: entry.audioPath || null,
      duration: entry.duration || 0,
      engine: entry.engine || null,
      modelId: entry.modelId || null,
      inferenceMs: entry.inferenceMs || null,
      sampleRate: entry.sampleRate || null,
      audioChannels: entry.audioChannels || null,
      formatMode: entry.formatMode || null,
      removeFillers: entry.removeFillers ?? false,
      britishEnglish: entry.britishEnglish ?? false,
      antiHallucination: entry.antiHallucination ?? false,
    });

    // Save segments if provided
    if (entry.segments && entry.segments.length > 0) {
      const segmentTuples = entry.segments.map(s => [
        s.start ?? s.startTime ?? 0,
        s.end ?? s.endTime ?? 0,
        s.text || '',
      ]);
      await invoke('save_segments', {
        transcriptId: entry.id,
        segments: segmentTuples,
      });
    }

    // Optimistic local update — add to front of list
    transcripts.unshift({
      id: entry.id,
      text: entry.text,
      source: entry.source,
      title: entry.title || null,
      audioPath: entry.audioPath || null,
      duration: entry.duration || 0,
      engine: entry.engine || null,
      modelId: entry.modelId || null,
      inferenceMs: entry.inferenceMs || null,
      sampleRate: entry.sampleRate || null,
      audioChannels: entry.audioChannels || null,
      formatMode: entry.formatMode || null,
      removeFillers: entry.removeFillers ?? false,
      britishEnglish: entry.britishEnglish ?? false,
      antiHallucination: entry.antiHallucination ?? false,
      createdAt: new Date().toISOString(),
      // Keep original fields for UI compatibility during migration
      date: entry.date || new Date().toLocaleString('en-GB'),
      preview: entry.preview || (entry.text || '').slice(0, 120),
      segments: entry.segments || [],
      language: entry.language,
      template: entry.template,
    });

    broadcastHistory();
    return true;
  } catch (e) {
    console.error('Failed to save transcript:', e);
    return false;
  }
}

/**
 * Delete a transcript by ID.
 * @param {string} id - Transcript ID
 */
export async function deleteTranscript(id) {
  try {
    await invoke('delete_transcript_by_id', { id });
    const idx = transcripts.findIndex(t => t.id === id);
    if (idx >= 0) transcripts.splice(idx, 1);
    broadcastHistory();
  } catch (e) {
    console.error('Failed to delete transcript:', e);
  }
}

/**
 * Full-text search across transcripts via FTS5.
 * Replaces the local state with search results.
 * @param {string} query - Search query
 * @param {number} [limit=50] - Maximum results
 */
export async function searchTranscripts(query, limit = 50) {
  if (!query || !query.trim()) {
    // Empty query — restore full list
    await loadHistory();
    return;
  }
  loading = true;
  searchActive = true;
  try {
    const result = await invoke('search_all_transcripts', {
      query: query.trim(),
      limit,
    });
    transcripts.length = 0;
    transcripts.push(...result);
  } catch (e) {
    // FTS5 can throw on malformed queries — fall back to full list
    console.error('Search failed, falling back to full list:', e);
    await loadHistory();
  } finally {
    loading = false;
  }
}

/** Get the reactive transcripts array. */
export function getHistory() {
  return transcripts;
}

/** Whether history is currently loading from the backend. */
export function getLoading() {
  return loading;
}

/** Whether a search filter is currently active. */
export function isSearchActive() {
  return searchActive;
}