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feature: Adds ZincReader and tests
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‎Sources/Haystack/IO/ZincReader.swift‎

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import Foundation
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public class ZincReader {
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let tokenizer: ZincTokenizer
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var cur: ZincToken = .eof
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var curVal: any Val = null
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var curLine: Int = 0
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var peek: ZincToken = .eof
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var peekVal: any Val = null
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var peekLine: Int = 0
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public init(_ zinc: String) throws {
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tokenizer = ZincTokenizer(zinc)
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try consume()
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try consume()
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}
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public func readVal() throws -> any Val {
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var val: any Val = null
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if cur == .id, curVal.equals("ver") {
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val = try parseGrid()
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} else {
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val = try parseVal()
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}
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try verify(.eof)
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return val
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}
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public func readGrid() throws -> Grid {
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guard let grid = try readVal() as? Grid else {
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throw ZincReaderError.InputIsNotGrid
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}
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return grid
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}
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private func parseVal() throws -> any Val {
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if cur == .id {
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guard let id = curVal as? String else {
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throw ZincReaderError.IdValueIsNotString(curVal)
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}
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try consume(.id)
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// check for Coord or XStr
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if cur == .lparen {
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if peek == .num {
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return try parseCoord(id)
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} else {
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return try parseXStr(id)
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}
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}
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switch id {
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case "T": return true
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case "F": return false
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case "N": return null
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case "M": return marker
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case "R": return remove
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case "NA": return na
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case "NaN": return Number(val: .nan)
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case "INF": return Number(val: .infinity)
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default:
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throw ZincReaderError.UnexpectedId(id)
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}
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}
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if cur.isLiteral {
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return try parseLiteral()
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}
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// -INF
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if cur == .minus, peek == .id, peekVal.equals("INF") {
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try consume(.minus)
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try consume(.id)
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return Number(val: -1.0 * .infinity)
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}
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if cur == .lbracket {
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return try parseList()
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}
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if cur == .lbrace {
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return try parseDict()
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}
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if cur == .lt2 {
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return try parseGrid()
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}
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throw ZincReaderError.UnexpectedToken(cur)
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}
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private func parseCoord(_ id: String) throws -> Coord {
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guard id == "C" else {
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throw ZincReaderError.InvalidCoord
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}
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try consume(.lparen)
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let latitude = try consumeNumber()
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try consume(.comma)
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let longitude = try consumeNumber()
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try consume(.rparen)
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return Coord(lat: latitude.val, lng: longitude.val)
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}
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private func parseXStr(_ id: String) throws -> XStr {
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guard (id.first?.isLowercase ?? false) else {
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throw ZincReaderError.InvalidXStr
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}
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try consume(.lparen)
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let val = try consumeString()
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try consume(.rparen)
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return XStr(type: id, val: val)
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}
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private func parseLiteral() throws -> any Val {
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var val = self.curVal
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if cur == .ref, peek == .str {
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guard let refVal = curVal as? String, let dis = peekVal as? String else {
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throw ZincReaderError.InvalidRef
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}
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val = Ref(val: refVal, dis: dis)
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try consume(.ref)
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}
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try consume()
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return val
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}
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private func parseList() throws -> List {
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var elements = [any Val]()
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while cur != .rbracket, cur != .eof {
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try elements.append(parseVal())
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guard cur == .comma else {
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break
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}
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try consume(.comma)
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}
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try consume(.rbracket)
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return List(elements)
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}
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private func parseDict() throws -> Dict {
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var elements = [String: any Val]()
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let hasBraces = cur == .lbrace
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if hasBraces {
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try consume(.lbrace)
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}
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while cur == .id {
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let id = try consumeTagName()
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var val: any Val = marker
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if cur == .colon {
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try consume(.colon)
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val = try parseVal()
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}
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elements[id] = val
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}
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if hasBraces {
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try consume(.rbrace)
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}
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return Dict(elements)
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}
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private func parseGrid() throws -> Grid {
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let isNested = cur == .lt2
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if isNested {
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try consume(.lt2)
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if cur == .nl {
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try consume(.nl)
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}
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}
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// Check version
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guard cur == .id, curVal.equals("ver") else {
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throw ZincReaderError.GridDoesNotBeginWithVersion(curVal)
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}
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try consume()
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try consume(.colon)
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let version = try consumeString()
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guard version == "3.0" else {
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throw ZincReaderError.UnsupportedZincVersion(version)
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}
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// Metadata
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let builder = GridBuilder()
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if cur == .id {
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try builder.setMeta(parseDict().elements)
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}
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try consume(.nl)
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// Columns
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var numCols = 0
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while cur == .id {
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numCols += 1
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let name = try consumeTagName()
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var colMeta: [String: any Val]? = nil
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if cur == .id {
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colMeta = try parseDict().elements
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}
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try builder.addCol(name: name, meta: colMeta)
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guard cur == .comma else {
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break
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}
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try consume(.comma)
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}
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guard numCols > 0 else {
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throw ZincReaderError.GridHasNoColumns
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}
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try consume(.nl)
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// Rows
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while true {
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if cur == .nl || cur == .eof || (isNested && cur == .gt2) {
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break
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}
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var cells = [any Val]()
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for i in 0 ..< numCols {
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if cur == .comma || cur == .nl || cur == .eof {
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cells.append(null)
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} else {
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try cells.append(parseVal())
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}
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if i+1 < numCols {
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try consume(.comma)
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}
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}
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try builder.addRow(cells)
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if cur == .eof || (isNested && cur == .gt2) {
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break
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}
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try consume(.nl)
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}
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if cur == .nl {
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try consume(.nl)
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}
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if isNested {
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try consume(.gt2)
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}
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return builder.toGrid()
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}
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// MARK: Token Reads
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private func consumeTagName() throws -> String {
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try verify(.id)
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guard let id = curVal as? String else {
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throw ZincReaderError.IdValueIsNotString(curVal)
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}
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guard (id.first?.isLowercase ?? false) else {
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throw ZincReaderError.InvalidTagName
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}
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try consume(.id)
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return id
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}
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private func consumeNumber() throws -> Number {
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try verify(.num)
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guard let number = curVal as? Number else {
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throw ZincReaderError.NumValueIsNotNumber(curVal)
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}
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try consume(.num)
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return number
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}
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private func consumeString() throws -> String {
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try verify(.str)
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guard let number = curVal as? String else {
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throw ZincReaderError.StrValueIsNotString(curVal)
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}
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try consume(.str)
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return number
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}
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private func consume(_ expected: ZincToken? = nil) throws {
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if let expected = expected {
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try verify(expected)
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}
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cur = peek;
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curVal = peekVal;
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curLine = peekLine;
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peek = try tokenizer.next();
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peekVal = tokenizer.val;
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peekLine = tokenizer.line;
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}
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private func verify(_ expected: ZincToken) throws {
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if cur != expected {
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throw ZincReaderError.ExpectedToken(expected, not: cur)
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}
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}
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}
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enum ZincReaderError: Error {
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case ExpectedToken(ZincToken, not: ZincToken)
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case GridDoesNotBeginWithVersion(any Val)
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case GridHasNoColumns
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case IdValueIsNotString(any Val)
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case InvalidCoord
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case InvalidRef
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case InvalidTagName
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case InvalidXStr
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case NumValueIsNotNumber(any Val)
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case StrValueIsNotString(any Val)
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case UnexpectedId(String)
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case UnexpectedToken(ZincToken)
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case InputIsNotGrid
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case UnsupportedZincVersion(String)
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}

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