MongoView/MongoView/Views/JavaScriptEditorView.swift

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

import AppKit

class JavaScriptEditorView: NSTextView {
    
    var highlighter = JavaScriptHighlighter()
    private var isRehighlighting = false
    
    override var string: String {
        get {
            super.string
        }
        set {
            isRehighlighting = true
            super.string = newValue
            rehighlight()
        }
    }

    func rehighlight() {
        isRehighlighting = true
        highlighter.highlight(attributed: self.textStorage!)
        isRehighlighting = false
    }
    
    override func awakeFromNib() {
        super.awakeFromNib()
        
        textStorage!.delegate = self
    }
    
    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
    }
    
    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)
            rehighlight()
            super.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 "'", "\"", "`":
            if case .string(_) = highlighter.token(at: range.location) {
                return nil
            } else {
                return string
            }
        case "(":
            if case .string(_) = highlighter.token(at: range.location) {
                return nil
            } else {
                return ")"
            }
        case "[":
            if case .string(_) = highlighter.token(at: range.location) {
                return nil
            } else {
                return "]"
            }
        case "{":
            if range.location > 0 {
                let index = self.string.index(self.string.startIndex, offsetBy: range.location - 1)
                let prevChar = self.string.unicodeScalars[index]
                if prevChar == "$" {
                    return "}"
                }
            }
            if case .string(_) = highlighter.token(at: range.location) {
                return nil
            } else {
                return "}"
            }
        default:
            return nil
        }
    }

}

extension JavaScriptEditorView: NSTextStorageDelegate {
    func textStorage(_ textStorage: NSTextStorage, didProcessEditing editedMask: NSTextStorageEditActions, range editedRange: NSRange, changeInLength delta: Int) {
        guard editedMask.contains(.editedCharacters), !isRehighlighting else { return }
        if delta == 1 {
            if let char = Unicode.Scalar((textStorage.string as NSString).character(at: editedRange.location)),
                highlighter.inserted(character: char, index: editedRange.location) {
                return
            }
        } else if delta == -1 {
            if highlighter.removed(index: editedRange.location) {
                return
            }
        }
        
        rehighlight()
    }
}