//===----------------------------------------------------------------------===//
// Copyright © 2025 Apple Inc. and the container project authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//===----------------------------------------------------------------------===//

import ContainerNetworkService
import Containerization
import ContainerizationError
import ContainerizationExtras
import ContainerizationOCI
import Foundation
import TerminalProgress

public struct Utility {
    private static let infraImages = [
        ClientDefaults.get(key: .defaultBuilderImage),
        ClientDefaults.get(key: .defaultInitImage),
    ]

    public static func createContainerID(name: String?) -> String {
        guard let name else {
            return UUID().uuidString.lowercased()
        }
        return name
    }

    public static func isInfraImage(name: String) -> Bool {
        for infraImage in infraImages {
            if name == infraImage {
                return true
            }
        }
        return false
    }

    public static func trimDigest(digest: String) -> String {
        var digest = digest
        digest.trimPrefix("sha256:")
        if digest.count > 24 {
            digest = String(digest.prefix(24)) + "..."
        }
        return digest
    }

    public static func validEntityName(_ name: String) throws {
        let pattern = #"^[a-zA-Z0-9][a-zA-Z0-9_.-]+$"#
        let regex = try Regex(pattern)
        if try regex.firstMatch(in: name) == nil {
            throw ContainerizationError(.invalidArgument, message: "invalid entity name \(name)")
        }
    }

    public static func containerConfigFromFlags(
        id: String,
        image: String,
        arguments: [String],
        process: Flags.Process,
        management: Flags.Management,
        resource: Flags.Resource,
        registry: Flags.Registry,
        progressUpdate: @escaping ProgressUpdateHandler
    ) async throws -> (ContainerConfiguration, Kernel) {
        let requestedPlatform = Parser.platform(os: management.os, arch: management.arch)
        let scheme = try RequestScheme(registry.scheme)

        await progressUpdate([
            .setDescription("Fetching image"),
            .setItemsName("blobs"),
        ])
        let taskManager = ProgressTaskCoordinator()
        let fetchTask = await taskManager.startTask()
        let img = try await ClientImage.fetch(
            reference: image,
            platform: requestedPlatform,
            scheme: scheme,
            progressUpdate: ProgressTaskCoordinator.handler(for: fetchTask, from: progressUpdate)
        )

        // Unpack a fetched image before use
        await progressUpdate([
            .setDescription("Unpacking image"),
            .setItemsName("entries"),
        ])
        let unpackTask = await taskManager.startTask()
        try await img.getCreateSnapshot(
            platform: requestedPlatform,
            progressUpdate: ProgressTaskCoordinator.handler(for: unpackTask, from: progressUpdate))

        await progressUpdate([
            .setDescription("Fetching kernel"),
            .setItemsName("binary"),
        ])

        let kernel = try await self.getKernel(management: management)

        // Pull and unpack the initial filesystem
        await progressUpdate([
            .setDescription("Fetching init image"),
            .setItemsName("blobs"),
        ])
        let fetchInitTask = await taskManager.startTask()
        let initImage = try await ClientImage.fetch(
            reference: ClientImage.initImageRef, platform: .current, scheme: scheme,
            progressUpdate: ProgressTaskCoordinator.handler(for: fetchInitTask, from: progressUpdate))

        await progressUpdate([
            .setDescription("Unpacking init image"),
            .setItemsName("entries"),
        ])
        let unpackInitTask = await taskManager.startTask()
        _ = try await initImage.getCreateSnapshot(
            platform: .current,
            progressUpdate: ProgressTaskCoordinator.handler(for: unpackInitTask, from: progressUpdate))

        await taskManager.finish()

        let imageConfig = try await img.config(for: requestedPlatform).config
        let description = img.description
        let pc = try Parser.process(
            arguments: arguments,
            processFlags: process,
            managementFlags: management,
            config: imageConfig
        )

        var config = ContainerConfiguration(id: id, image: description, process: pc)
        config.platform = requestedPlatform
        config.hostname = id

        config.resources = try Parser.resources(
            cpus: resource.cpus,
            memory: resource.memory
        )

        let tmpfs = try Parser.tmpfsMounts(management.tmpFs)
        let volumes = try Parser.volumes(management.volumes)
        var mounts = try Parser.mounts(management.mounts)
        mounts.append(contentsOf: tmpfs)
        mounts.append(contentsOf: volumes)
        config.mounts = mounts

        if management.networks.isEmpty {
            config.networks = [ClientNetwork.defaultNetworkName]
        } else {
            // networks may only be specified for macOS 26+
            guard #available(macOS 26, *) else {
                throw ContainerizationError(.invalidArgument, message: "non-default network configuration requires macOS 26 or newer")
            }
            config.networks = management.networks
        }

        var networkStatuses: [NetworkStatus] = []
        for networkName in config.networks {
            let network: NetworkState = try await ClientNetwork.get(id: networkName)
            guard case .running(_, let networkStatus) = network else {
                throw ContainerizationError(.invalidState, message: "network \(networkName) is not running")
            }
            networkStatuses.append(networkStatus)
        }

        let nameservers: [String]
        if management.dnsNameservers.isEmpty {
            let subnet = try CIDRAddress(networkStatuses[0].address)
            let nameserver = IPv4Address(fromValue: subnet.lower.value + 1).description
            nameservers = [nameserver]
        } else {
            nameservers = management.dnsNameservers
        }

        if management.dnsDisabled {
            config.dns = nil
        } else {
            let domain = management.dnsDomain ?? ClientDefaults.getOptional(key: .defaultDNSDomain)
            config.dns = .init(
                nameservers: nameservers,
                domain: domain,
                searchDomains: management.dnsSearchDomains,
                options: management.dnsOptions
            )
        }

        if Platform.current.architecture == "arm64" && requestedPlatform.architecture == "amd64" {
            config.rosetta = true
        }

        config.labels = try Parser.labels(management.labels)

        // Parse --publish-socket arguments and add to container configuration
        // to enable socket forwarding from container to host.
        config.publishedSockets = try Parser.publishSockets(management.publishSockets)

        return (config, kernel)
    }

    private static func getKernel(management: Flags.Management) async throws -> Kernel {
        // For the image itself we'll take the user input and try with it as we can do userspace
        // emulation for x86, but for the kernel we need it to match the hosts architecture.
        let s: SystemPlatform = .current
        if let userKernel = management.kernel {
            guard FileManager.default.fileExists(atPath: userKernel) else {
                throw ContainerizationError(.notFound, message: "Kernel file not found at path \(userKernel)")
            }
            let p = URL(filePath: userKernel)
            return .init(path: p, platform: s)
        }
        return try await ClientKernel.getDefaultKernel(for: s)
    }
}