import Foundation
import StableDiffusion
import StableDiffusionProtos

public actor ModelManager {
    private var modelInfos: [String: SdModelInfo] = [:]
    private var modelUrls: [String: URL] = [:]
    private var modelStates: [String: ModelState] = [:]

    private let modelBaseURL: URL

    public init(modelBaseURL: URL) {
        self.modelBaseURL = modelBaseURL
    }

    public func reloadAvailableModels() throws {
        modelInfos.removeAll()
        modelUrls.removeAll()
        modelStates.removeAll()
        let contents = try FileManager.default.contentsOfDirectory(at: modelBaseURL.resolvingSymlinksInPath(), includingPropertiesForKeys: [.isDirectoryKey])
        for subdirectoryURL in contents {
            let values = try subdirectoryURL.resourceValues(forKeys: [.isDirectoryKey])
            if values.isDirectory ?? false {
                try addModel(url: subdirectoryURL)
            }
        }
    }

    public func listAvailableModels() async throws -> [SdModelInfo] {
        var results: [SdModelInfo] = []
        for simpleInfo in modelInfos.values {
            var info = try SdModelInfo(jsonString: simpleInfo.jsonString())
            if let maybeLoaded = modelStates[info.name] {
                info.isLoaded = await maybeLoaded.isModelLoaded()
                if let loadedComputeUnits = await maybeLoaded.loadedModelComputeUnits() {
                    info.loadedComputeUnits = loadedComputeUnits
                }
            } else {
                info.isLoaded = false
                info.loadedComputeUnits = .init()
            }

            if info.attention == .splitEinSum {
                info.supportedComputeUnits = [
                    .cpuAndGpu,
                    .cpuAndNeuralEngine,
                    .cpu,
                    .all
                ]
            } else {
                info.supportedComputeUnits = [
                    .cpuAndGpu,
                    .cpu
                ]
            }

            results.append(info)
        }
        return results
    }

    public func createModelState(name: String) throws -> ModelState {
        let state = modelStates[name]
        let url = modelUrls[name]
        guard let url else {
            throw SdCoreError.modelNotFound
        }

        if state == nil {
            let state = ModelState(url: url)
            modelStates[name] = state
            return state
        } else {
            return state!
        }
    }

    public func getModelState(name: String) -> ModelState? {
        modelStates[name]
    }

    private func addModel(url: URL) throws {
        var info = SdModelInfo()
        info.name = url.lastPathComponent
        if let attention = getModelAttention(url) {
            info.attention = attention
        }
        modelInfos[info.name] = info
        modelUrls[info.name] = url
    }

    private func getModelAttention(_ url: URL) -> SdModelAttention? {
        let unetMetadataURL = url.appending(components: "Unet.mlmodelc", "metadata.json")

        struct ModelMetadata: Decodable {
            let mlProgramOperationTypeHistogram: [String: Int]
        }

        do {
            let jsonData = try Data(contentsOf: unetMetadataURL)
            let metadatas = try JSONDecoder().decode([ModelMetadata].self, from: jsonData)

            guard metadatas.count == 1 else {
                return nil
            }

            return metadatas[0].mlProgramOperationTypeHistogram["Ios16.einsum"] != nil ? SdModelAttention.splitEinSum : SdModelAttention.original
        } catch {
            return nil
        }
    }
}