// services/s3-service.mjs
import { S3Client, PutObjectCommand, ListObjectsV2Command, DeleteObjectsCommand } from '@aws-sdk/client-s3';
import { v4 as uuidv4 } from 'uuid';
import dotenv from 'dotenv';
import { logger } from '../utils/logger.mjs';
import { decodeBase64Image } from '../utils/image-processor.mjs';

dotenv.config();

const S3_ENDPOINT = process.env.S3_ENDPOINT;
const S3_REGION = process.env.S3_REGION;
const S3_ACCESS_KEY_ID = process.env.S3_ACCESS_KEY_ID;
const S3_SECRET_ACCESS_KEY = process.env.S3_SECRET_ACCESS_KEY;
const BUCKET_NAME = process.env.S3_BUCKET_NAME;
const PUBLIC_URL_FILE_PREFIX = (process.env.S3_PUBLIC_URL_PREFIX || 'files').replace(/\/$/, ''); // Ensures no trailing slash

let s3Client;

if (S3_ENDPOINT && S3_REGION && S3_ACCESS_KEY_ID && S3_SECRET_ACCESS_KEY && BUCKET_NAME) {
    s3Client = new S3Client({
        endpoint: S3_ENDPOINT,
        region: S3_REGION,
        credentials: {
            accessKeyId: S3_ACCESS_KEY_ID,
            secretAccessKey: S3_SECRET_ACCESS_KEY,
        },
        forcePathStyle: true, // Important for MinIO and some S3-compatibles
    });
} else {
    logger.warn('S3 client configuration is incomplete. S3 operations will be disabled.');
}


/**
 * Uploads an image from a base64 string to S3.
 * @param {string} base64Data The base64 content (without the data URI prefix).
 * @param {string} originalFormat The image format (e.g., 'png', 'jpeg').
 * @param {string} activityId The activity ID, used for naming.
 * @returns {Promise<string|null>} The public URL of the uploaded image or null on error.
 */
export async function uploadImageFromBase64(base64Data, originalFormat, activityId) {
    if (!s3Client) {
        logger.warn('S3 client not configured. Cannot upload image.');
        return null;
    }
    if (!base64Data || !originalFormat || !activityId) {
        logger.error('S3 Upload: Missing base64Data, originalFormat, or activityId');
        return null;
    }

    try {
        const imageBuffer = decodeBase64Image(base64Data);
        // Ensure PUBLIC_URL_FILE_PREFIX is part of the key
        const objectKey = `${PUBLIC_URL_FILE_PREFIX}/activity-${activityId}-${uuidv4()}.${originalFormat}`;

        const params = {
            Bucket: BUCKET_NAME,
            Key: objectKey,
            Body: imageBuffer,
            ContentType: `image/${originalFormat}`,
            ACL: 'public-read',
        };

        await s3Client.send(new PutObjectCommand(params));
        const publicUrl = constructS3Url(objectKey);
        logger.info(`Image uploaded to S3: ${publicUrl}`);
        return publicUrl;
    } catch (error) {
        logger.error(`S3 Upload Error for activity ${activityId}:`, error);
        return null;
    }
}

/**
 * Lists all objects in the S3 bucket under a specific prefix.
 * @param {string} prefix The prefix to filter objects by (e.g., S3_PUBLIC_URL_PREFIX + '/').
 * @returns {Promise<Array<string>>} A list of object keys.
 */
export async function listS3Objects(prefix) {
    if (!s3Client) {
        logger.warn('S3 client not configured. Cannot list objects.');
        return [];
    }
    const objectKeys = [];
    let isTruncated = true;
    let continuationToken;

    logger.debug(`Listing objects from S3 with prefix: "${prefix}"`);
    const listCommandInput = { // Renamed to avoid conflict if command is redefined in loop
        Bucket: BUCKET_NAME,
        Prefix: prefix,
    };

    try {
        while (isTruncated) {
            if (continuationToken) {
                listCommandInput.ContinuationToken = continuationToken;
            }
            const command = new ListObjectsV2Command(listCommandInput);
            const { Contents, IsTruncated: NextIsTruncated, NextContinuationToken } = await s3Client.send(command);
            
            if (Contents) {
                Contents.forEach(item => {
                    if (item.Key && !item.Key.endsWith('/')) { // Ensure it's a file, not a pseudo-directory
                       objectKeys.push(item.Key);
                    }
                });
            }
            isTruncated = NextIsTruncated;
            continuationToken = NextContinuationToken;
        }
        logger.info(`Listed ${objectKeys.length} object keys from S3 with prefix "${prefix}"`);
        return objectKeys;
    } catch (error) {
        logger.error(`S3 ListObjects Error with prefix "${prefix}":`, error);
        return [];
    }
}


/**
 * Deletes multiple objects from S3.
 * @param {Array<string>} objectKeysArray Array of object keys to delete.
 * @returns {Promise<boolean>} True if successful or partially successful, false on major error.
 */
export async function deleteS3Objects(objectKeysArray) {
    if (!s3Client) {
        logger.warn('S3 client not configured. Cannot delete objects.');
        return false;
    }
    if (!objectKeysArray || objectKeysArray.length === 0) {
        logger.info('No objects to delete from S3.');
        return true;
    }

    const MAX_DELETE_COUNT = 1000; // S3 API limit
    let allDeletionsSuccessful = true;

    for (let i = 0; i < objectKeysArray.length; i += MAX_DELETE_COUNT) {
        const chunk = objectKeysArray.slice(i, i + MAX_DELETE_COUNT);
        const deleteParams = {
            Bucket: BUCKET_NAME,
            Delete: {
                Objects: chunk.map(key => ({ Key: key })),
                Quiet: false, // We want error details
            },
        };
        try {
            const command = new DeleteObjectsCommand(deleteParams);
            const output = await s3Client.send(command);
            if (output.Errors && output.Errors.length > 0) {
                allDeletionsSuccessful = false;
                output.Errors.forEach(err => {
                    logger.error(`S3 Delete Error for key ${err.Key}: ${err.Message}`);
                });
            }
            if (output.Deleted && output.Deleted.length > 0) {
                 logger.info(`Successfully submitted deletion for ${output.Deleted.length} objects from S3 chunk (some might have failed, check individual errors).`);
            }
        } catch (error) {
            logger.error('S3 DeleteObjects Command Error for a chunk:', error);
            allDeletionsSuccessful = false;
        }
    }
    if (allDeletionsSuccessful && objectKeysArray.length > 0) {
        logger.info(`Finished S3 deletion request for ${objectKeysArray.length} keys.`);
    } else if (objectKeysArray.length > 0) {
        logger.warn(`S3 deletion request for ${objectKeysArray.length} keys completed with some errors.`);
    }
    return allDeletionsSuccessful;
}

/**
 * Constructs the public S3 URL for an object key.
 * @param {string} objectKey The key of the object in S3.
 * @returns {string} The full public URL.
 */
export function constructS3Url(objectKey) {
    // Ensure S3_ENDPOINT does not end with a slash
    const s3Base = S3_ENDPOINT.replace(/\/$/, '');
    // Ensure BUCKET_NAME does not start or end with a slash
    const bucket = BUCKET_NAME.replace(/^\//, '').replace(/\/$/, '');
    // Ensure objectKey does not start with a slash
    const key = objectKey.replace(/^\//, '');
    return `${s3Base}/${bucket}/${key}`;
}