import Configuration
import Hummingbird
import Infrastructure
import Logging
import Persistence
import WebsiteLibrary

package extension ConfigReader {

    // MARK: Type aliases

    /// The request context type the application serves its routes with; the security headers configuration is generic over it.
    typealias AppRequestContext = WebsiteRequestContext

    // MARK: Computed

    /// The `Cache-Control` policy applied to static files, grouped by media type.
    ///
    /// The max-ages are read from the `cache.maxAge.asset`, `cache.maxAge.text`, `cache.maxAge.image`, and
    /// `cache.maxAge.default` keys. Stylesheets and scripts are referenced through fingerprinted URLs (see `FingerprintAssets`) and
    /// fonts are immutable subset files, so all three are served long-lived and `immutable` — a deploy busts them by changing the URL, never by
    /// revalidation. The remaining text files (e.g. `robots.txt`) keep their unversioned URLs and require revalidation once stale; images and
    /// everything else are served public with their max-age alone. The groups match in order, so the specific types precede the `text` category.
    var cacheControl: CacheControl {
        let maxAgeAsset = int(
            forKey: .Cache.maxAgeAsset,
            default: .Cache.maxAgeAsset
        )
        let maxAgeDefault = int(
            forKey: .Cache.maxAgeDefault,
            default: .Cache.maxAgeDefault
        )
        let maxAgeImage = int(
            forKey: .Cache.maxAgeImage,
            default: .Cache.maxAgeImage
        )
        let maxAgeText = int(
            forKey: .Cache.maxAgeText,
            default: .Cache.maxAgeText
        )

        return .init([
            (.textCss, [.public, .maxAge(maxAgeAsset), .immutable]),
            (.textJavascript, [.public, .maxAge(maxAgeAsset), .immutable]),
            (.font, [.public, .maxAge(maxAgeAsset), .immutable]),
            (.text, [.public, .maxAge(maxAgeText), .mustRevalidate]),
            (.image, [.public, .maxAge(maxAgeImage)]),
            (.init(type: .any), [.public, .maxAge(maxAgeDefault)]),
        ])
    }

    /// The minimum response body size, in bytes, before a response is compressed — read from the `compression.minimumResponseSize` key.
    var compressionMinResponseSize: Int {
        int(
            forKey: .Compression.minResponseSize,
            default: .Compression.minResponseSize
        )
    }

    /// The persistence backend the service runs against, derived from the `database.*` keys.
    ///
    /// When `database.driver` selects PostgreSQL, the connection parameters are assembled from the `database.host`, `database.port`,
    /// `database.name`, `database.username`, `database.password` (empty when unset), `database.tls`,
    /// `database.pool.maxPerEventLoop`, and `database.pool.timeout` keys. Any other driver value falls back to the in-memory database.
    var driver: Driver {
        switch string(
            forKey: .Database.driver,
            default: .Database.driver
        ) {
        case .Database.driverPostgres:
            return .postgres(
                .init(
                    host: string(
                        forKey: .Database.host,
                        default: .Database.host
                    ),
                    port: int(
                        forKey: .Database.port,
                        default: .Database.port
                    ),
                    name: string(
                        forKey: .Database.name,
                        default: .Database.name
                    ),
                    username: string(
                        forKey: .Database.username,
                        default: .Database.username
                    ),
                    password: string(
                        forKey: .Database.password,
                        default: ""
                    ),
                    tls: tls,
                    maxConnectionsPerEventLoop: int(
                        forKey: .Database.poolMaxPerEventLoop,
                        default: .Database.poolMaxPerEventLoop
                    ),
                    poolTimeout: .seconds(int(
                        forKey: .Database.poolTimeout,
                        default: .Database.poolTimeout
                    ))
                )
            )
        default:
            return .inMemory
        }
    }

    /// The minimum log level the application emits at, read from the `log.level` key.
    ///
    /// Falls back to `.info` when the key is unset or its value names no `Logger.Level` case.
    var logLevel: Logger.Level {
        string(
            forKey: .Log.level,
            as: Logger.Level.self,
            default: .info
        )
    }

    /// Whether the executable runs in migrate-and-exit mode instead of serving, read from the `database.migrate` flag; off by default.
    var migrate: Bool {
        bool(
            forKey: .Database.migrate,
            default: false
        )
    }

    /// The rate limit applied to the subscription endpoint, built from the `rateLimit.*` keys.
    ///
    /// `rateLimit.limit` requests are admitted per client per `rateLimit.window` seconds. When `rateLimit.trustForwardedFor` is set,
    /// clients are keyed by the first `X-Forwarded-For` entry — enable it only behind a reverse proxy that sets the header, since clients can forge it
    /// otherwise.
    var rateLimit: RateLimitMiddleware<AppRequestContext>.Configuration {
        .init(
            limit: int(
                forKey: .RateLimit.limit,
                default: .RateLimit.limit
            ),
            window: .seconds(int(
                forKey: .RateLimit.window,
                default: .RateLimit.window
            )),
            trustForwardedFor: bool(
                forKey: .RateLimit.trustForwardedFor,
                default: false
            )
        )
    }

    /// The security headers middleware configuration, built from the `security.*` keys.
    ///
    /// Every header value has a default except `Strict-Transport-Security`, which is only sent when `security.strictTransportSecurity`
    /// is set — the header is a commitment browsers cache, so it must be opted into for deployments actually served over HTTPS.
    var securityHeaders: SecurityHeadersMiddleware<AppRequestContext>.Configuration {
        .init(
            contentSecurityPolicy: string(
                forKey: .Security.contentSecurityPolicy,
                default: .Security.contentSecurityPolicy
            ),
            contentTypeOptions: string(
                forKey: .Security.contentTypeOptions,
                default: .Security.contentTypeOptions
            ),
            frameOptions: string(
                forKey: .Security.frameOptions,
                default: .Security.frameOptions
            ),
            referrerPolicy: string(
                forKey: .Security.referrerPolicy,
                default: .Security.referrerPolicy
            ),
            permissionsPolicy: string(
                forKey: .Security.permissionsPolicy,
                default: .Security.permissionsPolicy
            ),
            strictTransportSecurity: string(
                forKey: .Security.strictTransportSecurity
            )
        )
    }

    /// The name the server reports in its `Server` response header, read from the `http.serverName` key.
    var serverName: String {
        string(
            forKey: .HTTP.serverName,
            default: .Server.name
        )
    }

    /// The directory the static files are served from, read from the `path.staticFiles` key.
    var staticFilesPath: String {
        string(
            forKey: .Path.staticFiles,
            default: .Path.staticResources
        )
    }

}

// MARK: - Helpers

private extension ConfigReader {

    // MARK: Properties

    /// The TLS posture for the PostgreSQL connection, mapped from the `database.tls` key: `off` and `require` map to their postures, and any
    /// other value falls back to `prefer`.
    var tls: TLS {
        switch string(
            forKey: .Database.tls,
            default: .Database.tls
        ) {
        case .Database.tlsOff: .off
        case .Database.tlsRequire: .require
        default: .prefer
        }
    }

}