import * as fs from 'fs'
import * as path from 'path'
import {pathToFileURL} from 'url'

import {CacheConfig, CacheProvider} from './configuration'
import {BasicCacheService} from './cache-service-basic'
import {BuildResult} from './build-results'
import {CacheOptions, CacheReport, CacheService} from './cache-service'
import {ProviderNote} from './caching-report'

const ENHANCED_CACHE_MESSAGE = `Enhanced Caching: This build is using the proprietary 'gradle-actions-caching' provider for optimized caching support. See https://github.com/gradle/actions/blob/main/DISTRIBUTION.md for terms of use and opt-out instructions.`

const BASIC_CACHE_MESSAGE = `Basic Caching: This build uses the basic open-source caching provider. For faster builds and advanced features, consider switching to the Enhanced Caching provider. See https://github.com/gradle/actions/blob/main/DISTRIBUTION.md for details.`

class NoOpCacheService implements CacheService {
    async restore(_gradleUserHome: string, _cacheOptions: CacheOptions): Promise<void> {
        return
    }

    async save(
        _gradleUserHome: string,
        _buildResults: BuildResult[],
        _cacheOptions: CacheOptions
    ): Promise<CacheReport> {
        return {status: 'disabled', entries: []}
    }
}

export async function getCacheService(cacheConfig: CacheConfig): Promise<CacheService> {
    if (cacheConfig.isCacheDisabled()) {
        logCacheMessage('Cache is disabled: will not restore state from previous builds.')
        return new NoOpCacheService()
    }

    if (cacheConfig.getCacheProvider() === CacheProvider.Basic) {
        logCacheMessage(BASIC_CACHE_MESSAGE)
        return new BasicCacheService()
    }

    logCacheMessage(ENHANCED_CACHE_MESSAGE)
    return loadVendoredCacheService()
}

/**
 * Identifies the caching provider for the Job Summary. Returns `undefined` when
 * caching is disabled, since no provider is engaged in that case.
 */
export function getProviderNote(cacheConfig: CacheConfig): ProviderNote | undefined {
    if (cacheConfig.isCacheDisabled()) {
        return undefined
    }
    return cacheConfig.getCacheProvider() === CacheProvider.Basic ? {kind: 'basic'} : {kind: 'enhanced'}
}

export async function loadVendoredCacheService(): Promise<CacheService> {
    const vendoredLibraryPath = findVendoredLibraryPath()
    const moduleUrl = pathToFileURL(vendoredLibraryPath).href
    return (await import(moduleUrl)) as CacheService
}

function findVendoredLibraryPath(): string {
    const moduleDir = import.meta.dirname
    const absolutePath = path.resolve(moduleDir, '../../../sources/vendor/gradle-actions-caching/index.js')

    if (fs.existsSync(absolutePath)) {
        return absolutePath
    }

    throw new Error(`Unable to locate vendored cache library at ${absolutePath}.`)
}

export function logCacheMessage(message: string): void {
    console.info(message)
}