import { randomUUID } from "node:crypto";
import {
  copyFileSync,
  existsSync,
  mkdirSync,
  readFileSync,
  readdirSync,
  rmSync,
  statSync,
} from "node:fs";
import path from "node:path";
import Database from "better-sqlite3";
import { backupDatabase } from "./backup-database.mjs";

const root = path.join(process.cwd(), ".test-databases");
const directory = path.join(root, `backup-restore-${randomUUID()}`);
if (!path.resolve(directory).startsWith(`${path.resolve(root)}${path.sep}`)) {
  throw new Error("Unsafe disposable backup verification path");
}
mkdirSync(directory, { recursive: true });
const sourcePath = path.join(directory, "source.test.db");
const backupPath = path.join(directory, "backup.test.db");
const restoredPath = path.join(directory, "restored.test.db");
let source;

function rowCounts(database) {
  const tables = database
    .prepare(
      "SELECT name FROM sqlite_master WHERE type = 'table' AND name NOT LIKE 'sqlite_%' ORDER BY name"
    )
    .all()
    .map((row) => row.name);
  return Object.fromEntries(
    tables.map((table) => [
      table,
      database.prepare(`SELECT COUNT(*) AS count FROM ${JSON.stringify(table)}`).get().count,
    ])
  );
}

try {
  source = new Database(sourcePath);
  source.pragma("foreign_keys = ON");
  source.pragma("journal_mode = WAL");
  source.pragma("wal_autocheckpoint = 0");
  const migrations = readdirSync(path.join(process.cwd(), "prisma", "migrations"), {
    withFileTypes: true,
  })
    .filter((entry) => entry.isDirectory())
    .map((entry) => entry.name)
    .sort();
  for (const migration of migrations) {
    source.exec(
      readFileSync(
        path.join(process.cwd(), "prisma", "migrations", migration, "migration.sql"),
        "utf8"
      )
    );
  }
  source.transaction(() => {
    source
      .prepare('INSERT INTO "Class" ("id", "name", "slug", "sortOrder") VALUES (?, ?, ?, ?)')
      .run("backup-class", "Representative content", "representative-content", 0);
    source
      .prepare(
        'INSERT INTO "MaterialGroup" ("id", "classId", "name", "type", "sortOrder") VALUES (?, ?, ?, ?, ?)'
      )
      .run("backup-group", "backup-class", "Backup group", "DECK", 0);
    source
      .prepare(
        'INSERT INTO "Deck" ("id", "classId", "groupId", "name", "description", "sortOrder") VALUES (?, ?, ?, ?, ?, ?)'
      )
      .run(
        "backup-deck",
        "backup-class",
        "backup-group",
        "Backup deck",
        "Restore drill content",
        0
      );
    source
      .prepare(
        'INSERT INTO "Flashcard" ("id", "deckId", "front", "back", "sortOrder") VALUES (?, ?, ?, ?, ?)'
      )
      .run("backup-card", "backup-deck", "Representative front", "Representative back", 0);
    source
      .prepare(
        'INSERT INTO "QuizSet" ("id", "classId", "name", "description", "sortOrder") VALUES (?, ?, ?, ?, ?)'
      )
      .run("backup-quiz", "backup-class", "Backup quiz", "Quiz relationship", 0);
    source
      .prepare(
        'INSERT INTO "Question" ("id", "quizSetId", "type", "prompt", "rationale", "category", "sortOrder") VALUES (?, ?, ?, ?, ?, ?, ?)'
      )
      .run(
        "backup-question",
        "backup-quiz",
        "MULTIPLE_CHOICE",
        "Representative prompt",
        "Representative rationale",
        "backup",
        0
      );
    source
      .prepare(
        'INSERT INTO "AnswerOption" ("id", "questionId", "text", "isCorrect", "sortOrder") VALUES (?, ?, ?, ?, ?)'
      )
      .run("backup-option", "backup-question", "Correct option", 1, 0);
    source
      .prepare(
        'INSERT INTO "SpacedRepetitionSet" ("id", "classId", "name", "sortOrder", "updatedAt") VALUES (?, ?, ?, ?, ?)'
      )
      .run("backup-srs", "backup-class", "Backup SRS", 0, Date.now());
    source
      .prepare(
        'INSERT INTO "SpacedRepetitionSetDeck" ("setId", "deckId", "sortOrder") VALUES (?, ?, ?)'
      )
      .run("backup-srs", "backup-deck", 0);
    source
      .prepare(
        'INSERT INTO "ShareLink" ("id", "targetType", "groupId") VALUES (?, ?, ?)'
      )
      .run("backup-share", "GROUP", "backup-group");
  })();

  const walPath = `${sourcePath}-wal`;
  if (!existsSync(walPath) || statSync(walPath).size === 0) {
    throw new Error("Backup drill did not create an active WAL database");
  }
  const sourceWalBytes = statSync(walPath).size;
  const sourceCounts = rowCounts(source);
  await backupDatabase(sourcePath, backupPath);
  copyFileSync(backupPath, restoredPath);
  source.close();
  source = undefined;

  const restored = new Database(restoredPath, { readonly: true, fileMustExist: true });
  try {
    const integrity = restored.pragma("integrity_check", { simple: true });
    const foreignKeyErrors = restored.pragma("foreign_key_check");
    const restoredCounts = rowCounts(restored);
    const representative = restored
      .prepare(`
        SELECT c.name AS className, g.name AS groupName, d.description,
               f.front, s.name AS setName, sl.targetType
        FROM "Class" c
        JOIN "MaterialGroup" g ON g.classId = c.id
        JOIN "Deck" d ON d.groupId = g.id
        JOIN "Flashcard" f ON f.deckId = d.id
        JOIN "SpacedRepetitionSetDeck" sd ON sd.deckId = d.id
        JOIN "SpacedRepetitionSet" s ON s.id = sd.setId
        JOIN "ShareLink" sl ON sl.groupId = g.id
        WHERE d.id = ?
      `)
      .get("backup-deck");
    const quizRelationship = restored
      .prepare(`
        SELECT q.name AS quizName, question.prompt, option.text, option.isCorrect
        FROM "QuizSet" q
        JOIN "Question" question ON question.quizSetId = q.id
        JOIN "AnswerOption" option ON option.questionId = question.id
        WHERE q.id = ?
      `)
      .get("backup-quiz");
    if (
      integrity !== "ok" ||
      foreignKeyErrors.length !== 0 ||
      JSON.stringify(restoredCounts) !== JSON.stringify(sourceCounts) ||
      representative?.description !== "Restore drill content" ||
      representative?.setName !== "Backup SRS" ||
      representative?.targetType !== "GROUP" ||
      quizRelationship?.isCorrect !== 1
    ) {
      throw new Error("Restored database did not preserve integrity, counts, content, and relationships");
    }
    console.info(
      JSON.stringify(
        {
          method: "better-sqlite3 online backup while the WAL source remained open",
          sourceWalBytes,
          integrity,
          foreignKeyErrors,
          counts: restoredCounts,
          representative,
          quizRelationship,
        },
        null,
        2
      )
    );
  } finally {
    restored.close();
  }
} finally {
  source?.close();
  rmSync(directory, { recursive: true, force: true });
}