import TestsUtils
public let CSVParsing = BenchmarkInfo(
    name: "CSVParsing",
    runFunction: run_CSVParsing,
    tags: [.miniapplication, .api, .String],
    setUpFunction: { buildWorkload() },
    tearDownFunction: nil)
public let CSVParsingAlt = BenchmarkInfo(
    name: "CSVParsingAlt",
    runFunction: run_CSVParsingAlt,
    tags: [.miniapplication, .api, .String],
    setUpFunction: { buildWorkload() },
    tearDownFunction: nil)
public let CSVParsingAltIndices = BenchmarkInfo(
    name: "CSVParsingAltIndices",
    runFunction: run_CSVParsingAltIndices,
    tags: [.miniapplication, .api, .String],
    setUpFunction: { buildWorkload() },
    tearDownFunction: nil)

struct ParseError: Error {
    var message: String
}

let comma = ",".utf16.first!
let newline = "\n".utf16.first!
let carriageReturn = "\n".utf16.first!
let quote = "\"".utf16.first!

func parseQuotedField(_ remainder: inout Substring) throws -> Substring? {
    var result: Substring = "" // we accumulate the result

    while !remainder.isEmpty {
        guard let nextQuoteIndex = remainder.firstIndex(of: "\"") else {
            throw ParseError(message: "Expected a closing \"")
        }

        // Append until the next quote
        result += remainder.prefix(upTo: nextQuoteIndex)
        remainder.remove(upToAndIncluding: nextQuoteIndex)

        if let peek = remainder.utf16.first {
            switch peek {
            case quote: // two quotes after each other is an escaped quote
                remainder.removeFirst()
                result.append("\"")
            case comma: // field ending
                remainder.removeFirst()
                return result
            default:
                return result
            }
        } else {
            // End of the string
            return result
        }
    }

    throw ParseError(message: "Expected a closing quote")
}

// Consume a single field from `remainder`
func parseField(_ remainder: inout Substring) throws -> Substring? {
    guard let start = remainder.utf16.first else { return nil }
    switch start {
    case quote:
        remainder.removeFirst() // remove the first quote
        return try parseQuotedField(&remainder)
    case newline:
        return nil
    default:
        // This is the most common case and should ideally be super fast...
        var index = remainder.utf16.startIndex
        while index < remainder.utf16.endIndex {
            switch remainder.utf16[index] {
            case comma:
                defer { remainder.remove(upToAndIncluding: index) }
                return remainder.prefix(upTo: index)
            case newline:
                let result = remainder.prefix(upTo: index)
                remainder.remove(upTo: index)
                return result
            default:
                remainder.utf16.formIndex(after: &index)
            }
        }
        let result = remainder
        remainder.removeAll()
        return result
    }
}

extension Substring {
    mutating func remove(upTo index: Index) {
        self = suffix(from: index)
    }

    mutating func remove(upToAndIncluding index: Index) {
        self = suffix(from: self.index(after: index))
    }
}

// Consume a single line from `remainder`
func parseLine<State>(_ remainder: inout Substring, result: inout State, processField: (inout State, Int, Substring) -> ()) throws -> Bool {
    var fieldNumber = 0

    while let field = try parseField(&remainder) {
        processField(&result, fieldNumber, field)
        fieldNumber += 1
    }

    if !remainder.isEmpty {
        let next = remainder.utf16[remainder.utf16.startIndex]
        guard next == carriageReturn || next == newline else {
            throw ParseError(message: "Expected a newline or CR, got \(next)")
        }

        while let x = remainder.utf16.first, x == carriageReturn || x == newline {
            remainder.utf16.removeFirst()
        }
    }

    return !remainder.isEmpty && fieldNumber > 0
}

extension String {
    func parseAlt() -> [[String]] {
        var result: [[String]] = [[]]
        var currentField = "".unicodeScalars
        var inQuotes = false

        func flush() {
            result[result.endIndex-1].append(String(currentField))
            currentField.removeAll()
        }

        for c in self.unicodeScalars {
            switch (c, inQuotes) {
            case (",", false):
                flush()
            case ("\n", false):
                flush()
                result.append([])
            case ("\"", _):
                inQuotes = !inQuotes
                currentField.append(c)
            default:
                currentField.append(c)
            }
        }
        flush()
        return result
    }
   func parseAltIndices() -> [[Substring]] {
        var result: [[Substring]] = [[]]
        var fieldStart = self.startIndex
        var inQuotes = false

        func flush(endingAt end: Index) {
            result[result.endIndex-1].append(self[fieldStart..<end])
        }

        for i in self.unicodeScalars.indices {
            switch (self.unicodeScalars[i], inQuotes) {
            case (",", false):
                flush(endingAt: i)
                fieldStart = self.unicodeScalars.index(after: i)
            case ("\n", false):
                flush(endingAt: i)
                fieldStart = self.unicodeScalars.index(after: i)
                result.append([])
            case ("\"", _):
                inQuotes = !inQuotes
            default:
                continue
            }
        }
        flush(endingAt: endIndex)
        return result
    }
}


let workloadBase = """
    Heading1,Heading2,Heading3,Heading4,Heading5,Heading6,Heading7
    FirstEntry,"secondentry",third,fourth,fifth,sixth,seventh
    zéro,un,deux,trois,quatre,cinq,six
    pagh,wa',cha',wej,IoS,vagh,jav
    ᬦᬸᬮ᭄,ᬲᬶᬓᬶ,ᬤᬸᬯ,ᬢᭂᬮᬸ,ᬧᬧᬢ᭄,ᬮᬶᬫᬾ,ᬦᭂᬦᭂᬫ᭄
    unu,du,tri,kvar,kvin,ses,sep
    "quoted", "f""i"e"l"d, "with a comma ',' in it", "and some \n for good measure", five, six, seven
    𐌏𐌉𐌍𐌏,𐌃𐌏,𐌕𐌓𐌉,𐌐𐌄𐌕𐌏𐌓,𐌐𐌄𐌌𐌐𐌄,𐌔𐌖𐌄𐌊𐌏𐌔,𐌔𐌄𐌗𐌕𐌀𐌌
    zero,un,duo.tres.quantro,cinque,sex
    nolla,yksi,kaksi,kolme,neljä,viisi,kuusi
    really long field, because otherwise, small string opt,imizations may trivial,ize the copies that, were trying to also, measure here!!!!
    нула,једин,два,три,четыри,петь,шесть
    一,二,三,四,五,六,七,
    saquui,ta'lo,tso'i,nvgi,hisgi,sudali,galiquogi
    """
let targetRowNumber = 200_000
let repeatCount = targetRowNumber / workloadBase.split(separator: "\n").count
let workload: String = repeatElement(workloadBase, count: repeatCount).joined()

public func buildWorkload() {
    let contents = workload
    let alt: [[String]] = contents.parseAlt()
    let altIndices: [[String]] = contents.parseAltIndices().map {
        $0.map { String($0) }
    }
    CheckResults(alt.elementsEqual(altIndices))
}

@inline(never)
public func run_CSVParsing(_ N: Int) {
    let contents = workload

    for _ in 0..<N {
        var remainder = contents[...]

        var result: Int = 0
        var x: () = ()

        while !remainder.isEmpty {
            blackHole(try? parseLine(&remainder, result: &x, processField: { state, _, field in
                ()
            }))
            blackHole(x)
            result += 1
        }
        blackHole(result)
    }
}

@inline(never)
public func run_CSVParsingAlt(_ N: Int) {
    let contents = workload
    for _ in 0..<N {
        blackHole(contents.parseAlt())
    }
}

@inline(never)
public func run_CSVParsingAltIndices(_ N: Int) {
    let contents = workload
    for _ in 0..<N {
        blackHole(contents.parseAltIndices())
    }
}