import "server-only";
import path from "node:path";
import { rawDb } from "@/lib/db/client";
import { clearAppSettingsCache } from "@/lib/db/appSettings";

const DB_PATH = path.join(process.cwd(), "data", "library.db");

const WIPE_ORDER = [
  "actress_categories_map",
  "collection_images",
  "image_tags",
  "image_genres",
  "image_actresses",
  "tags",
  "tag_categories",
  "genres",
  "actresses",
  "actress_categories",
  "collections",
  "series",
  "labels",
  "studios",
  "images",
  "app_settings",
];

const INSERT_ORDER = [
  "studios",
  "labels",
  "series",
  "actresses",
  "genres",
  "tag_categories",
  "tags",
  "actress_categories",
  "images",
  "collections",
  "image_actresses",
  "image_genres",
  "image_tags",
  "collection_images",
  "actress_categories_map",
  "app_settings",
];

function escIdent(s: string): string {
  return `"${s.replace(/"/g, '""')}"`;
}

function tableColumns(schema: "main" | "restore", table: string): string[] {
  try {
    const rows = rawDb.prepare(`PRAGMA ${schema}.table_info(${escIdent(table)})`).all() as Array<{ name: string }>;
    return rows.map((r) => r.name);
  } catch {
    return [];
  }
}

export type ImportDbResult = {
  ok: boolean;
  counts: Record<string, number>;
  errors: Array<{ table: string; message: string }>;
  snapshotPath: string | null;
  error?: string;
};

export async function importDatabaseTables(
  tables: Record<string, unknown[]>,
): Promise<ImportDbResult> {
  const counts: Record<string, number> = {};
  const errors: Array<{ table: string; message: string }> = [];

  let snapshotPath: string | null = null;
  try {
    const ts = new Date().toISOString().replace(/[:.]/g, "-");
    snapshotPath = `${DB_PATH}.${ts}.bak`;
    await rawDb.backup(snapshotPath);
  } catch (e) {
    return {
      ok: false,
      counts,
      errors,
      snapshotPath: null,
      error: `Failed to snapshot DB before import: ${(e as Error).message}`,
    };
  }

  rawDb.pragma("foreign_keys = OFF");
  try {
    const tx = rawDb.transaction(() => {
      for (const t of WIPE_ORDER) {
        try {
          rawDb.prepare(`DELETE FROM ${escIdent(t)}`).run();
          rawDb.prepare(`DELETE FROM sqlite_sequence WHERE name = ?`).run(t);
        } catch (e) {
          const msg = (e as Error).message ?? "";
          if (!/no such table/i.test(msg)) {
            throw new Error(`Wipe failed on ${t}: ${msg}`);
          }
        }
      }

      for (const t of INSERT_ORDER) {
        const rows = tables[t];
        if (!Array.isArray(rows) || rows.length === 0) {
          counts[t] = 0;
          continue;
        }
        const sample = rows[0] as Record<string, unknown>;
        const cols = Object.keys(sample);
        if (cols.length === 0) {
          counts[t] = 0;
          continue;
        }
        const colList = cols.map(escIdent).join(",");
        const placeholders = cols.map(() => "?").join(",");
        const stmt = rawDb.prepare(
          `INSERT INTO ${escIdent(t)} (${colList}) VALUES (${placeholders})`,
        );
        let inserted = 0;
        for (let rowIndex = 0; rowIndex < rows.length; rowIndex++) {
          const r = rows[rowIndex];
          if (!r || typeof r !== "object") continue;
          const row = r as Record<string, unknown>;
          const values = cols.map((c) => {
            const v = row[c];
            if (v === undefined) return null;
            if (typeof v === "boolean") return v ? 1 : 0;
            return v as null | string | number | bigint | Buffer;
          });
          try {
            stmt.run(...values);
            inserted++;
          } catch (e) {
            const message = `Insert failed on ${t} row ${rowIndex + 1}: ${(e as Error).message}`;
            errors.push({ table: t, message });
            throw new Error(message);
          }
        }
        counts[t] = inserted;
      }
    });
    tx();
  } catch (e) {
    rawDb.pragma("foreign_keys = ON");
    return {
      ok: false,
      counts,
      errors,
      snapshotPath,
      error: (e as Error).message,
    };
  }
  rawDb.pragma("foreign_keys = ON");
  clearAppSettingsCache();

  return { ok: true, counts, errors, snapshotPath };
}

export async function restoreDatabaseSnapshot(snapshotPath: string): Promise<void> {
  rawDb.pragma("foreign_keys = OFF");
  try {
    rawDb.prepare("ATTACH DATABASE ? AS restore").run(snapshotPath);
    const tx = rawDb.transaction(() => {
      for (const t of WIPE_ORDER) {
        try {
          rawDb.prepare(`DELETE FROM ${escIdent(t)}`).run();
          rawDb.prepare(`DELETE FROM sqlite_sequence WHERE name = ?`).run(t);
        } catch (e) {
          const msg = (e as Error).message ?? "";
          if (!/no such table/i.test(msg)) throw e;
        }
      }

      for (const t of INSERT_ORDER) {
        const mainCols = tableColumns("main", t);
        const restoreCols = new Set(tableColumns("restore", t));
        const cols = mainCols.filter((c) => restoreCols.has(c));
        if (cols.length === 0) continue;
        const colList = cols.map(escIdent).join(",");
        rawDb.prepare(`
          INSERT INTO ${escIdent(t)} (${colList})
          SELECT ${colList} FROM restore.${escIdent(t)}
        `).run();
      }
    });
    tx();
  } finally {
    try {
      rawDb.prepare("DETACH DATABASE restore").run();
    } catch {}
    rawDb.pragma("foreign_keys = ON");
    clearAppSettingsCache();
  }
}