import AppKit
import Combine
import Foundation

@MainActor
final class PunctuationCheckerViewModel: ObservableObject {
    static let maxWords = 1_000

    @Published var text: String = ""
    @Published private(set) var correctedText: String = ""
    @Published private(set) var issues: [GrammarIssue] = []
    @Published private(set) var hasResults = false
    @Published private(set) var isChecking = false
    @Published private(set) var errorMessage: String?

    private let punctuationCheckService: any PunctuationCheckServicing
    private let textExtractionService: any TextExtracting

    init(
        punctuationCheckService: any PunctuationCheckServicing = PunctuationCheckService(),
        textExtractionService: any TextExtracting = TextExtractionService()
    ) {
        self.punctuationCheckService = punctuationCheckService
        self.textExtractionService = textExtractionService
    }

    var wordCountLimitLabel: String {
        "\(text.wordCount)/\(Self.maxWords)"
    }

    var canCheck: Bool {
        !text.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty && !isChecking
    }

    func pasteText() {
        guard let clipboard = NSPasteboard.general.string(forType: .string) else { return }
        text = WordLimit.applyImported(clipboard, maxWords: Self.maxWords, setError: { errorMessage = $0 })
        resetResults()
    }

    func uploadFile() {
        Task {
            do {
                guard let extracted = try await textExtractionService.pickAndExtractText() else { return }
                text = WordLimit.applyImported(extracted, maxWords: Self.maxWords, setError: { errorMessage = $0 })
                resetResults()
            } catch {
                errorMessage = error.localizedDescription
            }
        }
    }

    func notifyWordLimitReached() {
        errorMessage = WordLimit.message(maxWords: Self.maxWords)
    }

    func handleTextChange() {
        let (limited, exceeded) = WordLimit.apply(text, maxWords: Self.maxWords)
        if exceeded {
            text = limited
            errorMessage = WordLimit.message(maxWords: Self.maxWords)
        } else if errorMessage == WordLimit.message(maxWords: Self.maxWords) {
            errorMessage = nil
        }
        if hasResults {
            resetResults()
        }
    }

    func clearText() {
        text = ""
        resetResults()
    }

    func resetResults() {
        correctedText = ""
        issues = []
        hasResults = false
        errorMessage = nil
    }

    func checkPunctuation() {
        let content = text.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !content.isEmpty else {
            resetResults()
            return
        }

        isChecking = true
        errorMessage = nil

        Task {
            do {
                let result = try await punctuationCheckService.checkPunctuation(in: content)
                correctedText = result.correctedText
                issues = result.issues
                hasResults = true
            } catch {
                errorMessage = error.localizedDescription
            }

            isChecking = false
        }
    }

    func copyCorrectedText() {
        guard !correctedText.isEmpty else { return }
        NSPasteboard.general.clearContents()
        NSPasteboard.general.setString(correctedText, forType: .string)
    }
}