import {
    existsSync,
    mkdirSync,
    statSync,
    symlinkSync,
    writeFileSync,
} from "node:fs";
import { join, relative, extname } from "node:path";
import type { Client } from "./client.js";
import type { EnteFile } from "./model/types.js";

export interface BackupError {
    fileID: number;
    title: string;
    collection: string;
    error: string;
}

export interface BackupResult {
    totalFiles: number;
    downloaded: number;
    skipped: number;
    failed: number;
    errors: BackupError[];
}

export type ProgressCallback = (message: string) => void;

const sanitizePath = (name: string): string =>
    name.replace(/[/\\:*?"<>|]/g, "_").replace(/^\.+/, "_");

const originalFileName = (file: EnteFile): string => {
    const ext = extname(file.metadata.title || "") || ".bin";
    return `${file.id}${ext}`;
};

export const runBackup = async (
    client: Client,
    outDir: string,
    onProgress?: ProgressCallback,
): Promise<BackupResult> => {
    const log = onProgress ?? (() => {});

    mkdirSync(outDir, { recursive: true });
    const originalsDir = join(outDir, "originals");
    mkdirSync(originalsDir, { recursive: true });
    const collectionsDir = join(outDir, "collections");
    mkdirSync(collectionsDir, { recursive: true });

    log("Fetching collections...");
    const collections = await client.listCollections();
    const downloadedIDs = new Set<number>();

    let totalFiles = 0;
    let downloaded = 0;
    let skipped = 0;
    let failed = 0;
    const errors: BackupError[] = [];

    for (const col of collections) {
        const colDirName = sanitizePath(col.name || `collection-${col.id}`);
        const colDir = join(collectionsDir, colDirName);
        mkdirSync(colDir, { recursive: true });

        log(`[${col.name}] Fetching file list...`);
        const files = await client.listFiles(col.id, col.key);
        log(`[${col.name}] ${files.length} file(s)`);

        const collectionMeta: {
            id: number;
            name: string;
            type: string;
            files: { id: number; metadata: EnteFile["metadata"] }[];
        } = {
            id: col.id,
            name: col.name,
            type: col.type,
            files: [],
        };

        for (const file of files) {
            totalFiles++;
            const origName = originalFileName(file);
            const origPath = join(originalsDir, origName);
            const linkName = sanitizePath(
                file.metadata.title || `file-${file.id}`,
            );
            const linkPath = join(colDir, linkName);

            if (!downloadedIDs.has(file.id)) {
                if (existsSync(origPath) && statSync(origPath).size > 0) {
                    skipped++;
                    downloadedIDs.add(file.id);
                } else {
                    try {
                        log(`[${col.name}] Downloading ${linkName}...`);
                        await client.downloadFile(file, origPath);
                        downloaded++;
                        downloadedIDs.add(file.id);
                    } catch (err) {
                        log(
                            `[${col.name}] FAILED ${linkName}: ${err instanceof Error ? err.message : err}`,
                        );
                        failed++;
                        errors.push({
                            fileID: file.id,
                            title: file.metadata.title,
                            collection: col.name,
                            error:
                                err instanceof Error
                                    ? err.message
                                    : String(err),
                        });
                        continue;
                    }
                }
            }

            // Write per-file metadata JSON alongside the original
            const metaJsonPath = join(originalsDir, `${file.id}.json`);
            if (!existsSync(metaJsonPath)) {
                const fileMeta: Record<string, unknown> = {
                    id: file.id,
                    collectionID: file.collectionID,
                    ownerID: file.ownerID,
                    metadata: file.metadata,
                };
                if (file.magicMetadata) {
                    fileMeta.magicMetadata = file.magicMetadata;
                }
                if (file.pubMagicMetadata) {
                    fileMeta.pubMagicMetadata = file.pubMagicMetadata;
                }
                writeFileSync(metaJsonPath, JSON.stringify(fileMeta, null, 2));
            }

            if (!existsSync(linkPath) && existsSync(origPath)) {
                const target = relative(colDir, origPath);
                symlinkSync(target, linkPath);
            }

            collectionMeta.files.push({
                id: file.id,
                metadata: file.metadata,
            });
        }

        writeFileSync(
            join(collectionsDir, `${colDirName}.json`),
            JSON.stringify(collectionMeta, null, 2),
        );
    }

    return { totalFiles, downloaded, skipped, failed, errors };
};