// Author: Simon-Pierre Boucher — contact@spboucher.ai
//
// Finds and validates the forge binary: a candidate is accepted only if
// `forge info` runs and reports a device — the same probe surfaces the GPU
// name for the header. Paths persist in UserDefaults.
import Foundation

struct ForgeValidation: Equatable, Sendable {
    var version: String   // device line, e.g. "Apple M5 Max"
    var binaryPath: String
}

enum ForgeBinaryLocator {
    static let defaultsKey = "forge.binary.path"
    static let workspaceKey = "forge.workspace.path"

    static var savedBinaryURL: URL? {
        UserDefaults.standard.string(forKey: defaultsKey).map { URL(fileURLWithPath: $0) }
    }

    static var savedWorkspaceURL: URL? {
        UserDefaults.standard.string(forKey: workspaceKey).map { URL(fileURLWithPath: $0) }
    }

    static func save(binary: URL) {
        UserDefaults.standard.set(binary.path, forKey: defaultsKey)
    }

    static func save(workspace: URL) {
        UserDefaults.standard.set(workspace.path, forKey: workspaceKey)
    }

    /// Candidate locations, most specific first.
    static func candidates() -> [URL] {
        var urls: [URL] = []
        if let saved = savedBinaryURL { urls.append(saved) }
        let home = FileManager.default.homeDirectoryForCurrentUser
        urls.append(home.appendingPathComponent("Desktop/forge/build/forge"))
        urls.append(URL(fileURLWithPath: "/usr/local/bin/forge"))
        return urls.filter { FileManager.default.isExecutableFile(atPath: $0.path) }
    }

    /// Runs `forge info` and parses the device line.
    static func validate(binary: URL) async -> Result<ForgeValidation, Error> {
        let runner = ProcessRunner()
        do {
            let (lines, exit) = try await runner.launch(
                executable: binary, arguments: ["info"],
                currentDirectory: binary.deletingLastPathComponent())
            var device = ""
            for await (line, _) in lines where line.hasPrefix("device: ") {
                device = String(line.dropFirst("device: ".count))
            }
            let status = await exit.value
            guard status.code == 0, !device.isEmpty else {
                throw NSError(domain: "ForgeStudio", code: 1, userInfo: [
                    NSLocalizedDescriptionKey:
                        "forge info a échoué (code \(status.code)). Vérifiez que forge.metallib est à côté du binaire.",
                ])
            }
            return .success(ForgeValidation(version: device, binaryPath: binary.path))
        } catch {
            return .failure(error)
        }
    }
}