import * as core from '@actions/core'
import * as cache from '@actions/cache'
import * as github from '@actions/github'
import * as crypto from 'crypto'

export function isCacheDisabled(): boolean {
    return core.getBooleanInput('cache-disabled')
}

export function isCacheReadOnly(): boolean {
    return core.getBooleanInput('cache-read-only')
}

export function isCacheDebuggingEnabled(): boolean {
    return process.env['CACHE_DEBUG_ENABLED'] ? true : false
}

function generateCacheKey(cacheName: string): CacheKey {
    // Prefix can be used to force change all cache keys
    const cacheKeyPrefix = process.env['CACHE_KEY_PREFIX'] || ''

    // At the most general level, share caches for all executions on the same OS
    const runnerOs = process.env['RUNNER_OS'] || ''
    const cacheKeyForOs = `${cacheKeyPrefix}${cacheName}|${runnerOs}`

    // Prefer caches that run this job
    const cacheKeyForJob = `${cacheKeyForOs}|${github.context.job}`

    // Prefer (even more) jobs that run this job with the same context (matrix)
    const cacheKeyForJobContext = `${cacheKeyForJob}[${determineJobContext()}]`

    // Exact match on Git SHA
    const cacheKey = `${cacheKeyForJobContext}-${github.context.sha}`

    return new CacheKey(cacheKey, [
        cacheKeyForJobContext,
        cacheKeyForJob,
        cacheKeyForOs
    ])
}

function determineJobContext(): string {
    // By default, we hash the full `matrix` data for the run, to uniquely identify this job invocation
    const workflowJobContext = core.getInput('workflow-job-context')
    return hashStrings([workflowJobContext])
}

export function hashStrings(values: string[]): string {
    const hash = crypto.createHash('md5')
    for (const value of values) {
        hash.update(value)
    }
    return hash.digest('hex')
}

class CacheKey {
    key: string
    restoreKeys: string[]

    constructor(key: string, restoreKeys: string[]) {
        this.key = key
        this.restoreKeys = restoreKeys
    }
}

export abstract class AbstractCache {
    private cacheName: string
    private cacheDescription: string
    private cacheKeyStateKey: string
    private cacheResultStateKey: string

    protected readonly cacheDebuggingEnabled: boolean

    constructor(cacheName: string, cacheDescription: string) {
        this.cacheName = cacheName
        this.cacheDescription = cacheDescription
        this.cacheKeyStateKey = `CACHE_KEY_${cacheName}`
        this.cacheResultStateKey = `CACHE_RESULT_${cacheName}`
        this.cacheDebuggingEnabled = isCacheDebuggingEnabled()
    }

    async restore(): Promise<void> {
        if (this.cacheOutputExists()) {
            core.info(
                `${this.cacheDescription} already exists. Not restoring from cache.`
            )
            return
        }

        const cacheKey = generateCacheKey(this.cacheName)

        core.saveState(this.cacheKeyStateKey, cacheKey.key)

        const cacheResult = await this.restoreCache(
            this.getCachePath(),
            cacheKey.key,
            cacheKey.restoreKeys
        )

        if (!cacheResult) {
            core.info(
                `${this.cacheDescription} cache not found. Will start with empty.`
            )
            return
        }

        core.saveState(this.cacheResultStateKey, cacheResult)

        core.info(
            `Restored ${this.cacheDescription} from cache key: ${cacheResult}`
        )

        await this.afterRestore()

        return
    }

    protected async restoreCache(
        cachePath: string[],
        cacheKey: string,
        cacheRestoreKeys: string[] = []
    ): Promise<string | undefined> {
        try {
            return await cache.restoreCache(
                cachePath,
                cacheKey,
                cacheRestoreKeys
            )
        } catch (error) {
            if (error instanceof cache.ValidationError) {
                // Validation errors should fail the build action
                throw error
            }
            // Warn about any other error and continue
            core.warning(`Failed to restore ${cacheKey}: ${error}`)
            return undefined
        }
    }

    protected async afterRestore(): Promise<void> {}

    async save(): Promise<void> {
        if (!this.cacheOutputExists()) {
            this.debug(`No ${this.cacheDescription} to cache.`)
            return
        }

        const cacheKey = core.getState(this.cacheKeyStateKey)
        const cacheResult = core.getState(this.cacheResultStateKey)

        if (!cacheKey) {
            this.debug(
                `${this.cacheDescription} existed prior to cache restore. Not saving.`
            )
            return
        }

        if (cacheResult && cacheKey === cacheResult) {
            core.info(
                `Cache hit occurred on the cache key ${cacheKey}, not saving cache.`
            )
            return
        }

        await this.beforeSave()

        core.info(
            `Caching ${this.cacheDescription} with cache key: ${cacheKey}`
        )
        const cachePath = this.getCachePath()
        await this.saveCache(cachePath, cacheKey)

        return
    }

    protected async beforeSave(): Promise<void> {}

    protected async saveCache(
        cachePath: string[],
        cacheKey: string
    ): Promise<void> {
        try {
            await cache.saveCache(cachePath, cacheKey)
        } catch (error) {
            if (error instanceof cache.ValidationError) {
                // Validation errors should fail the build action
                throw error
            } else if (error instanceof cache.ReserveCacheError) {
                // Reserve cache errors are expected if the artifact has been previously cached
                this.debug(error.message)
            } else {
                // Warn about any other error and continue
                core.warning(String(error))
            }
        }
    }

    protected debug(message: string): void {
        if (this.cacheDebuggingEnabled) {
            core.info(message)
        } else {
            core.debug(message)
        }
    }

    protected abstract cacheOutputExists(): boolean
    protected abstract getCachePath(): string[]
}