/**
 * @license
 * Copyright 2022-2026 Matter.js Authors
 * SPDX-License-Identifier: Apache-2.0
 */

import { Logger } from "#log/Logger.js";
import { MatterAggregateError } from "#MatterError.js";
import type { Storage } from "./Storage.js";

const logger = new Logger("StorageMigrator");

/**
 * A simple storage migrator of storage.
 *
 * It does not modify or remove source data.
 */
export namespace StorageMigration {
    export interface MigrationSkipped {
        contexts: string[];
        key: string;
        error: string;
    }

    export interface MigrationResult {
        success: boolean;
        migratedCount: number;
        skippedCount: number;
        skippedItems: MigrationSkipped[];
    }

    /**
     * Migrate storage from `source` to `target`.
     */
    export async function migrate(source: Storage, target: Storage): Promise<MigrationResult> {
        const result = {
            success: true,
            migratedCount: 0,
            skippedCount: 0,
            skippedItems: [],
        };

        // Migrate all contexts recursively
        await migrateContext({
            source,
            target,
            contexts: [],
            result,
        });

        // Result
        result.success = result.skippedCount === 0;
        return result;
    }

    /**
     * Export migration result to log
     */
    export function resultToLog(result: MigrationResult) {
        const timestamp = new Date().toISOString();

        let logContent = `
    # Migration Log
    - Timestamp: ${timestamp}
    - Success: ${result.success}
    - Migrated: ${result.migratedCount}
    - Skipped: ${result.skippedCount}
    `.replace(/^\s+/gm, "");
        if (result.skippedCount > 0 && result.skippedItems.length > 0) {
            logContent += `\n## Skipped Items\n`;
            for (const item of result.skippedItems) {
                logContent += `- ${buildContextKeyLog(item.contexts, item.key)}: ${item.error}\n`;
            }
        }

        return logContent;
    }
}

/**
 * Migrate a specific context and its sub-contexts recursively
 */
async function migrateContext(args: {
    source: Storage;
    target: Storage;
    contexts: string[];
    result: StorageMigration.MigrationResult;
}) {
    const { source, target, contexts, result } = args;
    const keys = await source.keys(contexts);

    for (const key of keys) {
        try {
            const value = await source.get(contexts, key);
            if (value === undefined) {
                // Blob
                const blob = await source.openBlob(contexts, key);
                if (blob.size === 0) {
                    continue;
                }

                const stream = blob.stream();
                await target.writeBlobFromStream(contexts, key, stream);

                result.migratedCount += 1;
                continue;
            }
            // Json
            await target.set(contexts, key, value);
            result.migratedCount += 1;
        } catch (err) {
            result.skippedCount += 1;
            result.skippedItems.push({
                contexts,
                key,
                error: err instanceof Error ? err.message : String(err),
            });
            logger.warn(`[migrate] Skipped '${buildContextKeyLog(contexts, key)}' entity: ${err}`);
        }
    }

    // Migrate subcontext recursively
    const subContexts = await source.contexts(contexts);
    const promises: Promise<void>[] = [];

    subContexts.forEach(subCon => {
        promises.push(
            migrateContext({
                ...args,
                contexts: [...contexts, subCon],
            }),
        );
    });

    // Promise.all with try catch
    await MatterAggregateError.allSettled(promises, "[migrate] Error migrating sub-contexts!");
}

function buildContextKeyLog(contexts: string[], key: string) {
    return `${contexts.join(".")}$${key}`;
}