import SwiftUI
import UIKit
import Runestone

// MARK: - CharacterPair concrete implementation
// CharacterPair is a protocol in Runestone — no concrete BasicCharacterPair exists.

private struct EditorCharacterPair: CharacterPair {
    let leading:  String
    let trailing: String
}

// MARK: - RunestoneEditorView

struct RunestoneEditorView: UIViewRepresentable {

    @Binding var content:     String
    @Binding var textViewRef: Runestone.TextView?
    let filePath:             String
    let theme:                any Theme
    let showLineNumbers:      Bool
    let lineWrapping:         Bool
    let indentWidth:          Int
    var diagnosticRanges:     [DiagnosticRange] = []
    var onContentChange:      ((String) -> Void)?
    var onCursorPositionChange: ((Int, Int) -> Void)?
    @ObservedObject var completionController: CompletionController

    func makeCoordinator() -> Coordinator { Coordinator(self) }

    func makeUIView(context: Context) -> Runestone.TextView {
        let tv = Runestone.TextView()
        configureAppearance(tv)
        configureEditing(tv)
        tv.editorDelegate = context.coordinator
        completionController.attach(to: tv)
        DispatchQueue.main.async { textViewRef = tv }
        loadState(into: tv)
        return tv
    }

    func updateUIView(_ tv: Runestone.TextView, context: Context) {
        if tv.text != content && !context.coordinator.isEditing {
            loadState(into: tv)
        }
        tv.showLineNumbers       = showLineNumbers
        tv.isLineWrappingEnabled = lineWrapping
        tv.indentStrategy        = indentWidth == 0
            ? .tab(length: 4)
            : .space(length: indentWidth)
        applyDiagnostics(to: tv)
    }

    private func loadState(into tv: Runestone.TextView) {
        let lang          = LanguageDetector.language(for: filePath)
        let capturedText  = content
        let capturedTheme = theme
        Task.detached(priority: .userInitiated) {
            // TextViewState init takes TreeSitterLanguage (non-optional).
            // Use two separate inits: one with language, one without (plain text).
            let state: TextViewState
            if let lang = lang {
                state = TextViewState(text: capturedText, theme: capturedTheme, language: lang)
            } else {
                state = TextViewState(text: capturedText, theme: capturedTheme)
            }
            await MainActor.run { tv.setState(state) }
        }
    }

    private func configureAppearance(_ tv: Runestone.TextView) {
        tv.backgroundColor       = UIColor(hex: "#1E1E1E")
        tv.showLineNumbers       = showLineNumbers
        tv.showSpaces            = false
        tv.showTabs              = false
        tv.showLineBreaks        = false
        tv.isLineWrappingEnabled = lineWrapping
        // highlightSelectedLine was replaced by lineSelectionDisplayType.
        // .line highlights the active line in the text area only.
        tv.lineSelectionDisplayType = .line
        tv.lineHeightMultiplier  = 1.4
        tv.kern                  = 0.3
        tv.contentInset          = UIEdgeInsets(top: 8, left: 0, bottom: 120, right: 0)
        tv.verticalOverscrollFactor = 0.5
    }

    private func configureEditing(_ tv: Runestone.TextView) {
        tv.isEditable            = true
        tv.autocorrectionType    = .no
        tv.autocapitalizationType = .none
        tv.smartDashesType       = .no
        tv.smartQuotesType       = .no
        tv.smartInsertDeleteType = .no
        tv.spellCheckingType     = .no
        tv.characterPairs = [
            EditorCharacterPair(leading: "(", trailing: ")"),
            EditorCharacterPair(leading: "[", trailing: "]"),
            EditorCharacterPair(leading: "{", trailing: "}"),
            EditorCharacterPair(leading: "\"", trailing: "\""),
        ]
        tv.characterPairTrailingComponentDeletionMode = .immediatelyFollowingLeadingComponent
        tv.indentStrategy = indentWidth == 0
            ? .tab(length: 4)
            : .space(length: indentWidth)
    }

    private func applyDiagnostics(to tv: Runestone.TextView) {
        guard !diagnosticRanges.isEmpty else {
            tv.highlightedRanges = []
            return
        }
        var highlights: [HighlightedRange] = []
        for diag in diagnosticRanges {
            // TextLocation is 0-indexed; compiler diagnostics are 1-indexed.
            let textLoc = TextLocation(lineNumber: diag.line - 1, column: diag.column - 1)
            guard let charOffset = tv.location(at: textLoc) else { continue }
            let nsRange = NSRange(location: charOffset, length: max(1, diag.length))
            let color: UIColor = diag.severity == .error
                ? UIColor(hex: "#F44747")
                : UIColor(hex: "#CCA700")
            // HighlightedRange only takes range and color — no cornerRadius/underlineStyle.
            highlights.append(HighlightedRange(range: nsRange, color: color))
        }
        tv.highlightedRanges = highlights
    }

    // MARK: - Coordinator

    @MainActor
    final class Coordinator: NSObject, TextViewDelegate {
        var parent:    RunestoneEditorView
        var isEditing: Bool = false

        init(_ parent: RunestoneEditorView) { self.parent = parent }

        func textViewDidChange(_ tv: Runestone.TextView) {
            isEditing = true
            parent.content = tv.text
            parent.onContentChange?(tv.text)
            parent.completionController.textDidChange(in: tv, filePath: parent.filePath)
            isEditing = false
        }

        func textViewDidChangeSelection(_ tv: Runestone.TextView) {
            let sel = tv.selectedRange
            if let loc = tv.textLocation(at: sel.location) {
                parent.onCursorPositionChange?(loc.lineNumber + 1, loc.column + 1)
            }
            if !isEditing { parent.completionController.dismiss() }
        }

        func textViewDidBeginEditing(_ tv: Runestone.TextView) {
            isEditing = true
        }

        func textViewDidEndEditing(_ tv: Runestone.TextView) {
            isEditing = false
            parent.completionController.dismiss()
        }
    }
}