import ChatService
import Environment
import Foundation
import GitHubCopilotService
import LanguageServerProtocol
import Logger
import OpenAIService
import SuggestionInjector
import SuggestionModel
import SuggestionWidget
import UserNotifications
import XPCShared

@ServiceActor
struct WindowBaseCommandHandler: SuggestionCommandHandler {
    nonisolated init() {}

    let presenter = PresentInWindowSuggestionPresenter()

    func presentSuggestions(editor: EditorContent) async throws -> UpdatedContent? {
        Task {
            do {
                try await _presentSuggestions(editor: editor)
            } catch let error as ServerError {
                Logger.service.error(error)
            } catch {
                presenter.presentError(error)
                Logger.service.error(error)
            }
        }
        return nil
    }

    private func _presentSuggestions(editor: EditorContent) async throws {
        presenter.markAsProcessing(true)
        defer {
            presenter.markAsProcessing(false)
        }
        let fileURL = try await Environment.fetchCurrentFileURL()
        let (workspace, filespace) = try await Workspace
            .fetchOrCreateWorkspaceIfNeeded(fileURL: fileURL)

        try Task.checkCancellation()

        let snapshot = Filespace.Snapshot(
            linesHash: editor.lines.hashValue,
            cursorPosition: editor.cursorPosition
        )

        // There is no need to regenerate suggestions for the same editor content.
        guard filespace.suggestionSourceSnapshot != snapshot else { return }

        try await workspace.generateSuggestions(
            forFileAt: fileURL,
            editor: editor
        )

        try Task.checkCancellation()

        if filespace.presentingSuggestion != nil {
            presenter.presentSuggestion(fileURL: fileURL)
        } else {
            presenter.discardSuggestion(fileURL: fileURL)
        }
    }

    func presentNextSuggestion(editor: EditorContent) async throws -> UpdatedContent? {
        Task {
            do {
                try await _presentNextSuggestion(editor: editor)
            } catch {
                presenter.presentError(error)
            }
        }
        return nil
    }

    private func _presentNextSuggestion(editor: EditorContent) async throws {
        presenter.markAsProcessing(true)
        defer { presenter.markAsProcessing(false) }
        let fileURL = try await Environment.fetchCurrentFileURL()
        let (workspace, filespace) = try await Workspace
            .fetchOrCreateWorkspaceIfNeeded(fileURL: fileURL)
        workspace.selectNextSuggestion(forFileAt: fileURL)

        if filespace.presentingSuggestion != nil {
            presenter.presentSuggestion(fileURL: fileURL)
        } else {
            presenter.discardSuggestion(fileURL: fileURL)
        }
    }

    func presentPreviousSuggestion(editor: EditorContent) async throws -> UpdatedContent? {
        Task {
            do {
                try await _presentPreviousSuggestion(editor: editor)
            } catch {
                presenter.presentError(error)
            }
        }
        return nil
    }

    private func _presentPreviousSuggestion(editor: EditorContent) async throws {
        presenter.markAsProcessing(true)
        defer { presenter.markAsProcessing(false) }
        let fileURL = try await Environment.fetchCurrentFileURL()
        let (workspace, filespace) = try await Workspace
            .fetchOrCreateWorkspaceIfNeeded(fileURL: fileURL)
        workspace.selectPreviousSuggestion(forFileAt: fileURL)

        if filespace.presentingSuggestion != nil {
            presenter.presentSuggestion(fileURL: fileURL)
        } else {
            presenter.discardSuggestion(fileURL: fileURL)
        }
    }

    func rejectSuggestion(editor: EditorContent) async throws -> UpdatedContent? {
        Task {
            do {
                try await _rejectSuggestion(editor: editor)
            } catch {
                presenter.presentError(error)
            }
        }
        return nil
    }

    private func _rejectSuggestion(editor: EditorContent) async throws {
        presenter.markAsProcessing(true)
        defer { presenter.markAsProcessing(false) }
        let fileURL = try await Environment.fetchCurrentFileURL()

        let dataSource = GraphicalUserInterfaceController.shared.widgetDataSource

        if await dataSource.promptToCodes[fileURL]?.promptToCodeService != nil {
            await dataSource.removePromptToCode(for: fileURL)
            presenter.closePromptToCode(fileURL: fileURL)
            return
        }

        let (workspace, _) = try await Workspace.fetchOrCreateWorkspaceIfNeeded(fileURL: fileURL)
        workspace.rejectSuggestion(forFileAt: fileURL, editor: editor)
        presenter.discardSuggestion(fileURL: fileURL)
    }

    func acceptSuggestion(editor: EditorContent) async throws -> UpdatedContent? {
        presenter.markAsProcessing(true)
        defer { presenter.markAsProcessing(false) }

        let fileURL = try await Environment.fetchCurrentFileURL()
        let (workspace, _) = try await Workspace.fetchOrCreateWorkspaceIfNeeded(fileURL: fileURL)

        let injector = SuggestionInjector()
        var lines = editor.lines
        var cursorPosition = editor.cursorPosition
        var extraInfo = SuggestionInjector.ExtraInfo()

        let dataSource = GraphicalUserInterfaceController.shared.widgetDataSource

        if let service = await dataSource.promptToCodes[fileURL]?.promptToCodeService {
            let suggestion = CodeSuggestion(
                text: service.code,
                position: service.selectionRange.start,
                uuid: UUID().uuidString,
                range: service.selectionRange,
                displayText: service.code
            )

            injector.acceptSuggestion(
                intoContentWithoutSuggestion: &lines,
                cursorPosition: &cursorPosition,
                completion: suggestion,
                extraInfo: &extraInfo
            )

            if service.isContinuous {
                service.selectionRange = .init(
                    start: service.selectionRange.start,
                    end: cursorPosition
                )
                presenter.presentPromptToCode(fileURL: fileURL)
            } else {
                await dataSource.removePromptToCode(for: fileURL)
                presenter.closePromptToCode(fileURL: fileURL)
            }

            return .init(
                content: String(lines.joined(separator: "")),
                newSelection: .init(start: service.selectionRange.start, end: cursorPosition),
                modifications: extraInfo.modifications
            )
        } else if let acceptedSuggestion = workspace.acceptSuggestion(
            forFileAt: fileURL,
            editor: editor
        ) {
            injector.acceptSuggestion(
                intoContentWithoutSuggestion: &lines,
                cursorPosition: &cursorPosition,
                completion: acceptedSuggestion,
                extraInfo: &extraInfo
            )

            presenter.discardSuggestion(fileURL: fileURL)

            return .init(
                content: String(lines.joined(separator: "")),
                newSelection: .cursor(cursorPosition),
                modifications: extraInfo.modifications
            )
        }

        return nil
    }

    func presentRealtimeSuggestions(editor: EditorContent) async throws -> UpdatedContent? {
        Task {
            try? await prepareCache(editor: editor)
        }
        return nil
    }

    func prepareCache(editor: EditorContent) async throws -> UpdatedContent? {
        let fileURL = try await Environment.fetchCurrentFileURL()
        let (_, filespace) = try await Workspace
            .fetchOrCreateWorkspaceIfNeeded(fileURL: fileURL)
        filespace.uti = editor.uti
        filespace.tabSize = editor.tabSize
        filespace.indentSize = editor.indentSize
        filespace.usesTabsForIndentation = editor.usesTabsForIndentation
        return nil
    }

    func generateRealtimeSuggestions(editor: EditorContent) async throws -> UpdatedContent? {
        return try await presentSuggestions(editor: editor)
    }

    func chatWithSelection(editor: EditorContent) async throws -> UpdatedContent? {
        Task {
            let viewStore = GraphicalUserInterfaceController.shared.viewStore
            viewStore.send(.openChatPanel(forceDetach: false))
        }
        return nil
    }

    func promptToCode(editor: EditorContent) async throws -> UpdatedContent? {
        Task {
            do {
                try await presentPromptToCode(
                    editor: editor,
                    extraSystemPrompt: nil,
                    prompt: nil,
                    isContinuous: false,
                    generateDescription: nil,
                    name: nil
                )
            } catch {
                presenter.presentError(error)
            }
        }
        return nil
    }

    func customCommand(id: String, editor: EditorContent) async throws -> UpdatedContent? {
        Task {
            do {
                try await handleCustomCommand(id: id, editor: editor)
            } catch {
                presenter.presentError(error)
            }
        }
        return nil
    }
}

extension WindowBaseCommandHandler {
    func handleCustomCommand(id: String, editor: EditorContent) async throws {
        struct CommandNotFoundError: Error, LocalizedError {
            var errorDescription: String? { "Command not found" }
        }

        let availableCommands = UserDefaults.shared.value(for: \.customCommands)
        guard let command = availableCommands.first(where: { $0.id == id })
        else { throw CommandNotFoundError() }

        switch command.feature {
        case .chatWithSelection, .customChat:
            Task { @MainActor in
                GraphicalUserInterfaceController.shared.viewStore
                    .send(.sendCustomCommandToActiveChat(command))
            }
        case let .promptToCode(extraSystemPrompt, prompt, continuousMode, generateDescription):
            try await presentPromptToCode(
                editor: editor,
                extraSystemPrompt: extraSystemPrompt,
                prompt: prompt,
                isContinuous: continuousMode ?? false,
                generateDescription: generateDescription,
                name: command.name
            )
        case let .oneTimeDialog(
            systemPrompt,
            overwriteSystemPrompt,
            prompt,
            receiveReplyInNotification
        ):
            try await executeOneTimeDialog(
                systemPrompt: systemPrompt,
                overwriteSystemPrompt: overwriteSystemPrompt ?? false,
                prompt: prompt ?? "",
                receiveReplyInNotification: receiveReplyInNotification ?? false
            )
        }
    }

    func presentPromptToCode(
        editor: EditorContent,
        extraSystemPrompt: String?,
        prompt: String?,
        isContinuous: Bool,
        generateDescription: Bool?,
        name: String?
    ) async throws {
        presenter.markAsProcessing(true)
        defer { presenter.markAsProcessing(false) }
        let fileURL = try await Environment.fetchCurrentFileURL()
        let (workspace, _) = try await Workspace
            .fetchOrCreateWorkspaceIfNeeded(fileURL: fileURL)
        guard workspace.isSuggestionFeatureEnabled else {
            presenter.presentErrorMessage("Prompt to code is disabled for this project")
            return
        }

        let codeLanguage = languageIdentifierFromFileURL(fileURL)

        let (code, selection) = {
            guard var selection = editor.selections.last,
                  selection.start != selection.end
            else { return ("", .cursor(editor.cursorPosition)) }

            let isMultipleLine = selection.start.line != selection.end.line
            let isSpaceOnlyBeforeStartPositionOnTheSameLine = {
                guard selection.start.line >= 0, selection.start.line < editor.lines.count else {
                    return false
                }
                let line = editor.lines[selection.start.line]
                guard selection.start.character > 0, selection.start.character < line.count else {
                    return false
                }
                let substring =
                    line[line.startIndex..<line
                        .index(line.startIndex, offsetBy: selection.start.character)]
                return substring.allSatisfy { $0.isWhitespace }
            }()

            if isMultipleLine || isSpaceOnlyBeforeStartPositionOnTheSameLine {
                // when there are multiple lines start from char 0 so that it can keep the
                // indentation.
                selection.start = .init(line: selection.start.line, character: 0)
            }
            return (
                editor.selectedCode(in: selection),
                .init(
                    start: .init(line: selection.start.line, character: selection.start.character),
                    end: .init(line: selection.end.line, character: selection.end.character)
                )
            )
        }() as (String, CursorRange)

        let dataSource = GraphicalUserInterfaceController.shared.widgetDataSource

        let promptToCode = await dataSource.createPromptToCode(
            for: fileURL,
            projectURL: workspace.projectRootURL,
            selectedCode: code,
            allCode: editor.content,
            selectionRange: selection,
            language: codeLanguage,
            extraSystemPrompt: extraSystemPrompt,
            generateDescriptionRequirement: generateDescription,
            name: name
        )

        promptToCode.isContinuous = isContinuous
        if let prompt, !prompt.isEmpty {
            Task { try await promptToCode.modifyCode(prompt: prompt) }
        }

        presenter.presentPromptToCode(fileURL: fileURL)
    }

    func executeOneTimeDialog(
        systemPrompt: String?,
        overwriteSystemPrompt: Bool,
        prompt: String,
        receiveReplyInNotification: Bool
    ) async throws {
        guard !prompt.isEmpty else { return }

        let service = ChatService()

        if let systemPrompt {
            if overwriteSystemPrompt {
                service.mutateSystemPrompt(systemPrompt)
            } else {
                service.mutateExtraSystemPrompt(systemPrompt)
            }
        }

        let result = try await service.sendAndWait(content: prompt)
        
        guard receiveReplyInNotification else { return }

        let granted = try await UNUserNotificationCenter.current()
            .requestAuthorization(options: [.alert])

        if granted {
            let content = UNMutableNotificationContent()
            content.title = "Reply"
            content.body = result
            let request = UNNotificationRequest(
                identifier: "reply",
                content: content,
                trigger: nil
            )
            do {
                try await UNUserNotificationCenter.current().add(request)
            } catch {
                presenter.presentError(error)
            }
        } else {
            presenter.presentErrorMessage("Notification permission is not granted.")
        }
    }
}