import { and, inArray, sql } from "drizzle-orm";
import { drizzle } from "drizzle-orm/node-postgres";
import fs from "node:fs/promises";
import { Pool, type QueryResult } from "pg";

import { schema } from "@/integrations/drizzle";
import { ReactiveResumeV4JSONImporter } from "@/integrations/import/reactive-resume-v4-json";
import { defaultResumeData } from "@/schema/resume/data";
import { generateId } from "@/utils/string";

// Types for the production database
type Visibility = "public" | "private";

interface ProductionResume {
  id: string;
  title: string;
  slug: string;
  data: unknown; // JSON data
  visibility: Visibility;
  locked: boolean;
  userId: string;
  createdAt: Date;
  updatedAt: Date;
}

interface ProductionStatistics {
  id: string;
  views: number;
  downloads: number;
  resumeId: string;
  createdAt: Date;
  updatedAt: Date;
}

const productionUrl = process.env.PRODUCTION_DATABASE_URL;
const localUrl = process.env.DATABASE_URL;

if (!productionUrl) throw new Error("PRODUCTION_DATABASE_URL is not set");
if (!localUrl) throw new Error("DATABASE_URL is not set");

const productionPool = new Pool({ connectionString: productionUrl });
const localPool = new Pool({ connectionString: localUrl });

const productionDb = drizzle({ client: productionPool });
const localDb = drizzle({ client: localPool, schema });

// == Persistent mapping file paths ==
const USER_ID_MAP_FILE = "./scripts/migration/user-id-map.json";
const RESUME_ID_MAP_FILE = "./scripts/migration/resume-id-map.json";

// == Progress checkpoint file path ==
const PROGRESS_FILE = "./scripts/migration/resume-progress.json";

// You may tune this for your use case
// Reduced from 10000 to avoid PostgreSQL message format errors
const BATCH_SIZE = 10_000;

// Chunk size for actual inserts - smaller to avoid PostgreSQL message size limits
// Especially important for resumes as they contain large JSONB data
const INSERT_CHUNK_SIZE = 1000;

// == Progress checkpoint interface ==
// Uses cursor-based pagination with (createdAt, id) composite key for efficiency
interface MigrationProgress {
  // Cursor for pagination - last seen createdAt timestamp
  lastSeenCreatedAt: string | null;
  // Cursor for pagination - last seen id (for tiebreaker when timestamps are equal)
  lastSeenId: string | null;
  resumesCreated: number;
  statisticsCreated: number;
  skipped: number;
  totalResumesProcessed: number;
  errors: number;
  lastUpdated: string;
}

// Flag to track if shutdown was requested
let shutdownRequested = false;

async function loadProgress(): Promise<MigrationProgress | null> {
  try {
    const text = await fs.readFile(PROGRESS_FILE, { encoding: "utf-8" });
    const progress = JSON.parse(text) as MigrationProgress;
    console.log(`📂 Found existing progress file. Last updated: ${progress.lastUpdated}`);
    console.log(`   Resuming from cursor (createdAt: ${progress.lastSeenCreatedAt}, id: ${progress.lastSeenId})...`);
    return progress;
  } catch (e) {
    console.warn("⚠️  Failed to load progress file, starting from beginning.", e);
  }
  return null;
}

async function saveProgress(progress: MigrationProgress): Promise<void> {
  try {
    progress.lastUpdated = new Date().toISOString();
    await fs.writeFile(PROGRESS_FILE, JSON.stringify(progress, null, 2), { encoding: "utf-8" });
    console.log(`💾 Progress saved at cursor (createdAt: ${progress.lastSeenCreatedAt}, id: ${progress.lastSeenId})`);
  } catch (e) {
    console.error("🚨 Failed to save progress:", e);
  }
}

async function clearProgress(): Promise<void> {
  try {
    await fs.unlink(PROGRESS_FILE);
    console.log("🗑️  Progress file cleared.");
  } catch {
    // Ignore errors when clearing
  }
}

async function loadUserIdMapFromFile(): Promise<Map<string, string>> {
  try {
    const text = await fs.readFile(USER_ID_MAP_FILE, { encoding: "utf-8" });
    const obj = JSON.parse(text);
    return new Map(Object.entries(obj));
  } catch (e) {
    console.warn("⚠️  Failed to load userIdMap from disk, continuing with empty map.", e);
  }
  return new Map<string, string>();
}

async function loadResumeIdMapFromFile(): Promise<Map<string, string>> {
  try {
    const text = await fs.readFile(RESUME_ID_MAP_FILE, { encoding: "utf-8" });
    const obj = JSON.parse(text);
    return new Map(Object.entries(obj));
  } catch (e) {
    console.warn("⚠️  Failed to load resumeIdMap from disk, continuing with empty map.", e);
  }
  return new Map<string, string>();
}

async function saveResumeIdMapToFile(resumeIdMap: Map<string, string>) {
  const obj: Record<string, string> = Object.fromEntries(resumeIdMap.entries());
  await fs.writeFile(RESUME_ID_MAP_FILE, JSON.stringify(obj, null, "\t"), { encoding: "utf-8" });
}

export async function migrateResumes() {
  const migrationStart = performance.now();
  console.log("⌛ Starting resume migration...");

  let hasMore = true;

  // Cursor-based pagination state
  let lastSeenCreatedAt: string | null = null;
  let lastSeenId: string | null = null;

  // Load persistent ID maps from file
  const userIdMap = await loadUserIdMapFromFile();
  const resumeIdMap = await loadResumeIdMapFromFile();

  // Track migration stats
  let resumesCreated = 0;
  let statisticsCreated = 0;
  let skipped = 0;
  let totalResumesProcessed = 0;
  let errors = 0;

  // Load saved progress if exists
  const savedProgress = await loadProgress();
  if (savedProgress) {
    lastSeenCreatedAt = savedProgress.lastSeenCreatedAt;
    lastSeenId = savedProgress.lastSeenId;
    resumesCreated = savedProgress.resumesCreated;
    statisticsCreated = savedProgress.statisticsCreated;
    skipped = savedProgress.skipped;
    totalResumesProcessed = savedProgress.totalResumesProcessed;
    errors = savedProgress.errors;
  }

  // Helper to get current progress object
  const getCurrentProgress = (): MigrationProgress => ({
    lastSeenCreatedAt,
    lastSeenId,
    resumesCreated,
    statisticsCreated,
    skipped,
    totalResumesProcessed,
    errors,
    lastUpdated: new Date().toISOString(),
  });

  // Setup graceful shutdown handler
  const handleShutdown = async () => {
    if (shutdownRequested) return;
    shutdownRequested = true;
    console.log("\n⚠️  Shutdown requested. Saving progress...");
    await saveProgress(getCurrentProgress());
    await saveResumeIdMapToFile(resumeIdMap);
    console.log("👋 Exiting. Run the script again to resume from where you left off.");
    process.exit(0);
  };

  process.on("exit", handleShutdown);

  // Initialize the importer
  const importer = new ReactiveResumeV4JSONImporter();

  while (hasMore) {
    // Check if shutdown was requested
    if (shutdownRequested) break;

    console.log(
      `📥 Fetching resumes batch from production database (cursor: createdAt=${lastSeenCreatedAt}, id=${lastSeenId})...`,
    );

    // Use cursor-based pagination for better performance
    // Tuple comparison syntax allows Postgres to use composite index efficiently
    let resumes: ProductionResume[];

    if (lastSeenCreatedAt && lastSeenId) {
      const result = (await productionDb.execute(sql`
				SELECT id, title, slug, data, visibility, locked, "userId", "createdAt", "updatedAt"
				FROM "Resume"
				WHERE ("createdAt", id) < (${lastSeenCreatedAt}::timestamp, ${lastSeenId})
				ORDER BY "createdAt" DESC, id DESC
				LIMIT ${BATCH_SIZE}
			`)) as unknown as QueryResult<ProductionResume>;
      resumes = result.rows;
    } else {
      const result = (await productionDb.execute(sql`
				SELECT id, title, slug, data, visibility, locked, "userId", "createdAt", "updatedAt"
				FROM "Resume"
				ORDER BY "createdAt" DESC, id DESC
				LIMIT ${BATCH_SIZE}
			`)) as unknown as QueryResult<ProductionResume>;
      resumes = result.rows;
    }

    console.log(`📋 Found ${resumes.length} resumes in this batch.`);

    if (resumes.length === 0) {
      hasMore = false;
      break;
    }

    // Fetch statistics only for these resumes in this batch
    const resumeIds = resumes.map((r) => r.id);

    // Drizzle does not interpolate arrays, so we join and use a custom SQL string
    // Escape single quotes in IDs (though UUIDs shouldn't contain them, this is safer)
    const resumeIdsForSql = resumeIds.map((id) => `'${id.replace(/'/g, "''")}'`).join(", ");

    const { rows: statistics } = (await productionDb.execute(sql`
			SELECT id, views, downloads, "resumeId", "createdAt", "updatedAt"
			FROM "Statistics"
			WHERE "resumeId" IN (${sql.raw(resumeIdsForSql)})
		`)) as unknown as QueryResult<ProductionStatistics>;

    // Create a map of resumeId -> statistics for quick lookup
    const statisticsMap = new Map<string, ProductionStatistics>();
    for (const stat of statistics) {
      statisticsMap.set(stat.resumeId, stat);
    }

    // Filter out resumes where userId is not in userIdMap
    const resumesToProcess = resumes
      .map((resume) => {
        const newUserId = userIdMap.get(resume.userId);
        if (!newUserId) {
          skipped++;
          return null;
        }
        return { resume, newUserId };
      })
      .filter((item): item is NonNullable<typeof item> => item !== null);

    if (resumesToProcess.length === 0) {
      console.log(`⏭️  All resumes in this batch have userIds not found in userIdMap.`);
      // Update cursor to the last resume in this batch
      const lastResume = resumes[resumes.length - 1];
      if (lastResume) {
        lastSeenCreatedAt =
          lastResume.createdAt instanceof Date ? lastResume.createdAt.toISOString() : String(lastResume.createdAt);
        lastSeenId = lastResume.id;
      }
      totalResumesProcessed += resumes.length;
      await saveProgress(getCurrentProgress());
      continue;
    }

    // Get unique userIds and bulk check if they exist in local database
    const uniqueUserIds = [...new Set(resumesToProcess.map((r) => r.newUserId))];
    const existingUsers = await localDb.select().from(schema.user).where(inArray(schema.user.id, uniqueUserIds));

    const existingUserIds = new Set(existingUsers.map((u) => u.id));

    // Filter out resumes where user doesn't exist
    const resumesWithValidUsers = resumesToProcess.filter(({ newUserId }) => {
      if (!existingUserIds.has(newUserId)) {
        skipped++;
        return false;
      }
      return true;
    });

    if (resumesWithValidUsers.length === 0) {
      console.log(`⏭️  All resumes in this batch have userIds not found in local database.`);
      // Update cursor to the last resume in this batch
      const lastResume = resumes[resumes.length - 1];
      if (lastResume) {
        lastSeenCreatedAt =
          lastResume.createdAt instanceof Date ? lastResume.createdAt.toISOString() : String(lastResume.createdAt);
        lastSeenId = lastResume.id;
      }
      totalResumesProcessed += resumes.length;
      await saveProgress(getCurrentProgress());
      continue;
    }

    // Bulk check for existing resumes (by slug + userId)
    // We need to check each unique combination
    const slugUserIdPairs = resumesWithValidUsers.map(({ resume, newUserId }) => ({
      slug: resume.slug,
      userId: newUserId,
    }));

    // Get all unique slugs and userIds
    const uniqueSlugs = [...new Set(slugUserIdPairs.map((p) => p.slug))];
    const userIdsForSlugCheck = [...new Set(slugUserIdPairs.map((p) => p.userId))];

    // Fetch all existing resumes that match any of our slugs and userIds
    const existingResumes = await localDb
      .select()
      .from(schema.resume)
      .where(and(inArray(schema.resume.slug, uniqueSlugs), inArray(schema.resume.userId, userIdsForSlugCheck)));

    // Create a set of existing slug+userId combinations
    const existingResumeKeys = new Set(existingResumes.map((r) => `${r.slug}:${r.userId}`));

    // Filter out resumes that already exist
    const resumesToInsert = resumesWithValidUsers.filter(({ resume, newUserId }) => {
      const key = `${resume.slug}:${newUserId}`;
      if (existingResumeKeys.has(key)) {
        skipped++;
        return false;
      }
      return true;
    });

    if (resumesToInsert.length === 0) {
      console.log(`⏭️  All resumes in this batch already exist in target DB.`);
      // Update cursor to the last resume in this batch
      const lastResume = resumes[resumes.length - 1];
      if (lastResume) {
        lastSeenCreatedAt =
          lastResume.createdAt instanceof Date ? lastResume.createdAt.toISOString() : String(lastResume.createdAt);
        lastSeenId = lastResume.id;
      }
      totalResumesProcessed += resumes.length;
      await saveProgress(getCurrentProgress());
      continue;
    }

    console.log(`📝 Preparing to bulk insert ${resumesToInsert.length} resumes...`);

    // Prepare bulk insert data
    const batchStart = performance.now();
    try {
      const resumesToInsertData = resumesToInsert.map(({ resume, newUserId }) => {
        // Transform the data using the V4 importer
        let transformedData = defaultResumeData;
        try {
          const dataJson = typeof resume.data === "string" ? resume.data : JSON.stringify(resume.data);
          transformedData = importer.parse(dataJson);
        } catch (error) {
          console.error(`⚠️  Failed to parse resume data for resume ${resume.id}, using default data:`, error);
          // Use default data if parsing fails
          transformedData = defaultResumeData;
        }

        // Map visibility to isPublic (visibility === "public" -> isPublic = true)
        const isPublic = resume.visibility === "public";

        const newResumeId = generateId();

        // Track the ID mapping for future reference
        resumeIdMap.set(resume.id, newResumeId);

        return {
          resumeData: {
            id: newResumeId,
            name: resume.title,
            slug: resume.slug,
            tags: [], // Default empty array
            isPublic: isPublic,
            isLocked: resume.locked,
            password: null, // No password in old schema
            data: transformedData,
            userId: newUserId,
            createdAt: resume.createdAt,
            updatedAt: resume.updatedAt,
          },
          originalResumeId: resume.id,
          newResumeId: newResumeId,
        };
      });

      // Bulk insert resumes (chunked to avoid PostgreSQL message size limits)
      // Resumes contain large JSONB data, so we use smaller chunks
      const resumeDataList = resumesToInsertData.map(({ resumeData }) => resumeData);
      for (let i = 0; i < resumeDataList.length; i += INSERT_CHUNK_SIZE) {
        const chunk = resumeDataList.slice(i, i + INSERT_CHUNK_SIZE);
        await localDb.insert(schema.resume).values(chunk);
      }
      resumesCreated += resumesToInsertData.length;

      // Prepare statistics for bulk insert
      const statisticsToInsert = resumesToInsertData
        .map(({ originalResumeId, newResumeId }) => {
          const resumeStatistics = statisticsMap.get(originalResumeId);
          if (!resumeStatistics) return null;

          return {
            id: generateId(),
            views: resumeStatistics.views,
            downloads: resumeStatistics.downloads,
            lastViewedAt: null, // Not available in old schema
            lastDownloadedAt: null, // Not available in old schema
            resumeId: newResumeId,
            createdAt: resumeStatistics.createdAt,
            updatedAt: resumeStatistics.updatedAt,
          };
        })
        .filter((stat): stat is NonNullable<typeof stat> => stat !== null);

      // Bulk insert statistics (chunked)
      if (statisticsToInsert.length > 0) {
        for (let i = 0; i < statisticsToInsert.length; i += INSERT_CHUNK_SIZE) {
          const chunk = statisticsToInsert.slice(i, i + INSERT_CHUNK_SIZE);
          await localDb.insert(schema.resumeStatistics).values(chunk);
        }
        statisticsCreated += statisticsToInsert.length;
      }

      const batchEnd = performance.now();
      const batchTimeMs = batchEnd - batchStart;
      console.log(
        `✅ Bulk inserted ${resumesToInsertData.length} resumes in ${batchTimeMs.toFixed(1)} ms (avg ${(batchTimeMs / resumesToInsertData.length).toFixed(1)} ms/resume)`,
      );

      // Save resume ID map after each successful batch
      await saveResumeIdMapToFile(resumeIdMap);
    } catch (error) {
      console.error(`🚨 Failed to bulk insert resumes batch:`, error);
      errors++;
      // Continue with next batch even if this one fails
    }

    // Update cursor to the last resume in this batch
    const lastResume = resumes[resumes.length - 1];
    if (lastResume) {
      lastSeenCreatedAt =
        lastResume.createdAt instanceof Date ? lastResume.createdAt.toISOString() : String(lastResume.createdAt);
      lastSeenId = lastResume.id;
    }

    totalResumesProcessed += resumes.length;
    console.log(`📦 Processed ${totalResumesProcessed} resumes so far...\n`);

    // Save progress after each batch
    await saveProgress(getCurrentProgress());
  }

  // Remove signal handlers
  process.off("exit", handleShutdown);

  const migrationEnd = performance.now();
  const migrationDurationMs = migrationEnd - migrationStart;

  console.log("\n📊 Migration Summary:");
  console.log(`   Resumes created: ${resumesCreated}`);
  console.log(`   Statistics created: ${statisticsCreated}`);
  console.log(`   Skipped (userId not found or already exist): ${skipped}`);
  console.log(`   Errors: ${errors}`);
  console.log(
    `⏱️  Total migration time: ${migrationDurationMs.toFixed(1)} ms (${(migrationDurationMs / 1000).toFixed(2)} seconds)`,
  );

  // Final save of the mapping (ensures up-to-date state)
  await saveResumeIdMapToFile(resumeIdMap);

  // Clear progress file on successful completion (only if not interrupted)
  if (!shutdownRequested) {
    await clearProgress();
    console.log("✅ Resume migration complete!");
  } else {
    console.log("⏸️  Migration paused. Run again to resume.");
  }
}

if (import.meta.main) {
  // Reset shutdown flag for fresh run
  shutdownRequested = false;

  try {
    await migrateResumes();
  } finally {
    await productionPool.end();
    await localPool.end();
  }
}