// ── Timer & Routine Export / Import ──────────────────────────
// Export all timers + routines as JSON, import from JSON file

import type { Timer } from './timer-engine';
import type { Routine } from './routines';

// ── Types ─────────────────────────────────────────────────────

export interface ExportData {
  version: 1;
  exportedAt: number;
  app: 'chronomind';
  timers: Timer[];
  routines?: Routine[];
}

export interface ImportResult {
  success: boolean;
  imported: number;
  skipped: number;
  errors: string[];
}

// ── Export ─────────────────────────────────────────────────────

/**
 * Export timers as a downloadable JSON blob.
 */
export function exportTimers(timers: Timer[]): ExportData {
  return {
    version: 1,
    exportedAt: Date.now(),
    app: 'chronomind',
    timers: timers.map((t) => ({ ...t })), // shallow clone
  };
}

/**
 * Export timers + routines as a downloadable JSON blob.
 */
export function exportAll(timers: Timer[], routines: Routine[]): ExportData {
  return {
    version: 1,
    exportedAt: Date.now(),
    app: 'chronomind',
    timers: timers.map((t) => ({ ...t })),
    routines: routines.map((r) => ({ ...r, steps: r.steps.map((s) => ({ ...s })) })),
  };
}

/**
 * Trigger a browser download of the export data.
 */
export function downloadExport(timers: Timer[]): void {
  const data = exportTimers(timers);
  const json = JSON.stringify(data, null, 2);
  const blob = new Blob([json], { type: 'application/json' });
  const url = URL.createObjectURL(blob);

  const a = document.createElement('a');
  a.href = url;
  a.download = `chronomind-export-${new Date().toISOString().slice(0, 10)}.json`;
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);
  URL.revokeObjectURL(url);
}

/**
 * Trigger a browser download of timers + routines.
 */
export function downloadExportAll(timers: Timer[], routines: Routine[]): void {
  const data = exportAll(timers, routines);
  const json = JSON.stringify(data, null, 2);
  const blob = new Blob([json], { type: 'application/json' });
  const url = URL.createObjectURL(blob);

  const a = document.createElement('a');
  a.href = url;
  a.download = `chronomind-export-${new Date().toISOString().slice(0, 10)}.json`;
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);
  URL.revokeObjectURL(url);
}

// ── Import ────────────────────────────────────────────────────

/**
 * Validate and parse an import file.
 */
export function parseImportData(jsonStr: string): ExportData | null {
  try {
    const data = JSON.parse(jsonStr);
    if (!data || data.app !== 'chronomind' || !Array.isArray(data.timers)) {
      return null;
    }
    return data as ExportData;
  } catch {
    return null;
  }
}

/**
 * Import timers from parsed export data, deduplicating by ID.
 */
export function importTimers(
  exportData: ExportData,
  existingTimers: Timer[]
): ImportResult {
  const errors: string[] = [];
  let imported = 0;
  let skipped = 0;

  const existingIds = new Set(existingTimers.map((t) => t.id));
  const newTimers: Timer[] = [];

  for (const timer of exportData.timers) {
    // Basic validation
    if (!timer.id || !timer.type || !timer.label) {
      errors.push(`Invalid timer: missing required fields (id, type, or label)`);
      skipped++;
      continue;
    }

    if (existingIds.has(timer.id)) {
      skipped++;
      continue;
    }

    // Validate required numeric fields
    if (typeof timer.createdAt !== 'number' || typeof timer.targetTime !== 'number') {
      errors.push(`Timer "${timer.label}": invalid timestamps`);
      skipped++;
      continue;
    }

    newTimers.push(timer);
    imported++;
  }

  return {
    success: errors.length === 0,
    imported,
    skipped,
    errors,
  };
}

/**
 * Import routines from parsed export data, deduplicating by ID.
 */
export function importRoutines(
  exportData: ExportData,
  existingRoutines: Routine[]
): ImportResult {
  if (!exportData.routines || exportData.routines.length === 0) {
    return { success: true, imported: 0, skipped: 0, errors: [] };
  }

  const errors: string[] = [];
  let imported = 0;
  let skipped = 0;

  const existingIds = new Set(existingRoutines.map((r) => r.id));

  for (const routine of exportData.routines) {
    if (!routine.id || !routine.name || !Array.isArray(routine.steps)) {
      errors.push(`Invalid routine: missing required fields (id, name, or steps)`);
      skipped++;
      continue;
    }

    if (existingIds.has(routine.id)) {
      skipped++;
      continue;
    }

    imported++;
  }

  return {
    success: errors.length === 0,
    imported,
    skipped,
    errors,
  };
}

/**
 * Read a File object and return the parsed content as string.
 */
export function readFileAsText(file: File): Promise<string> {
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onload = () => resolve(reader.result as string);
    reader.onerror = () => reject(new Error('Failed to read file'));
    reader.readAsText(file);
  });
}