JSON.StringRule.swift

internal import Grammar

extension JSON {
    /// Matches a string literal.
    ///
    /// String literals always begin and end with an ASCII double quote character (`"`).
    enum StringRule<Location> {
    }
}
extension JSON.StringRule: ParsingRule {
    typealias Terminal = UInt8

    static func parse<Source>(
        _ input: inout ParsingInput<some ParsingDiagnostics<Source>>
    ) throws -> String
        where   Source.Element == Terminal,
        Source.Index == Location {
        typealias DoubleQuote = UnicodeEncoding<Location, UInt8>.DoubleQuote

        try input.parse(as: DoubleQuote.self)

        let start: Location      = input.index
        input.parse(as: CodeUnit.self, in: Void.self)
        let end: Location        = input.index
        var string: String       = .init(decoding: input[start ..< end], as: Unicode.UTF8.self)

        while let next: String   = input.parse(as: EscapeSequence?.self) {
            string             += next
            let start: Location  = input.index
            input.parse(as: CodeUnit.self, in: Void.self)
            let end: Location    = input.index
            string             += .init(decoding: input[start ..< end], as: Unicode.UTF8.self)
        }

        try input.parse(as: DoubleQuote.self)
        return string
    }
}