//
//  JavaScriptEditorView.swift
//  MongoView
//
//  Created by Shadowfacts on 4/4/20.
//  Copyright © 2020 Shadowfacts. All rights reserved.
//

import AppKit

class JavaScriptEditorView: NSTextView {
    
    var highlighter: JavaScriptHighlighter?
    
    override var string: String {
        didSet {
            rehighlight()
        }
    }

    func rehighlight() {
        highlighter = JavaScriptHighlighter(mutableAttributed: self.textStorage!)
        highlighter!.highlight()
    }
    
    override func shouldChangeText(in affectedCharRange: NSRange, replacementString: String?) -> Bool {
        guard super.shouldChangeText(in: affectedCharRange, replacementString: replacementString) else {
            return false
        }
        
        if affectedCharRange.length == 0,
            let string = replacementString,
            string.count == 1,
            tryAutocompleteCharacter(for: affectedCharRange, string: string) {
            return false
        }

        return true
    }

    override func didChangeText() {
        rehighlight()
        
        super.didChangeText()
    }
    
    func tryAutocompleteCharacter(for range: NSRange, string inserted: String) -> Bool {
        if let end = autocompleteResultFor(string: inserted, in: range) {
            textStorage!.insert(NSAttributedString(string: "\(inserted)\(end)"), at: range.location)
            didChangeText()
            setSelectedRange(NSRange(location: range.location + 1, length: 0))
            return true
        } else {
            return false
        }
    }
    
    private func autocompleteResultFor(string: String, in range: NSRange) -> String? {
        switch string {
        case "'", "\"", "`":
            return token(at: range.location) != .string ? string : nil
        case "(":
            return token(at: range.location) != .string ? ")" : nil
        case "[":
            return token(at: range.location) != .string ? "]" : nil
        case "{":
            var prevChar: Unicode.Scalar?
            if range.location > 0 {
                let index = self.string.index(self.string.startIndex, offsetBy: range.location - 1)
                prevChar = self.string.unicodeScalars[index]
            }
            return token(at: range.location) != .string || (prevChar == "$") ? "}" : nil
        default:
            return nil
        }
    }

    private func token(at index: Int) -> JavaScriptHighlighter.TokenType? {
        guard let highlighter = highlighter else { return nil }
        for (token, range) in highlighter.tokens where range.contains(index) {
            return token
        }
        return nil
    }
}