PureYAML/Sources/Parsing/TokenEventParser.Block.swift

extension PureYAML.Parsing.TokenEventParser {
    mutating func parseBlockSequence(
        properties: PureYAML.Parsing.NodeProperties,
        allowMappingKeyTerminator: Bool = false,
    ) throws -> PureYAML.Parsing.NodeResult {
        let start = try expect("block sequence entry") { $0.isBlockEntry }
        let startMark = properties.mark ?? start.mark
        var endMark = start.endMark
        try emit(.sequenceStart(
            anchor: properties.anchor,
            tag: properties.tag,
            style: .block,
            mark: startMark,
        ))

        try parseBlockSequenceItem(
            after: start,
            endMark: &endMark,
            allowMappingKeyTerminator: allowMappingKeyTerminator,
        )
        try consumeSequenceItemBoundaryDedent(sequenceIndentWidth: start.mark.column - 1)
        try consumeSequenceItemBoundaryIndent(sequenceIndentWidth: start.mark.column - 1)
        while cursor.current?.kind.isBlockEntry == true {
            let entry = try expect("block sequence entry") { $0.isBlockEntry }
            try parseBlockSequenceItem(
                after: entry,
                endMark: &endMark,
                allowMappingKeyTerminator: allowMappingKeyTerminator,
            )
            try consumeSequenceItemBoundaryDedent(sequenceIndentWidth: entry.mark.column - 1)
            try consumeSequenceItemBoundaryIndent(sequenceIndentWidth: entry.mark.column - 1)
        }
        if let current = cursor.current, current.kind.isMappingKey, !allowMappingKeyTerminator {
            throw PureYAML.Parsing.ParseError.mixedCollectionStyles(line: current.mark.line)
        }

        try emit(.sequenceEnd(mark: endMark))
        return PureYAML.Parsing.NodeResult(kind: .sequence, endMark: endMark)
    }

    mutating func consumeSequenceItemBoundaryDedent(sequenceIndentWidth: Int) throws {
        guard dedentWidth(cursor.current) == sequenceIndentWidth,
              try cursor.peek()?.kind.isBlockEntry == true
        else {
            return
        }
        _ = try expect("dedent") { $0.isDedent }
    }

    mutating func consumeSequenceItemBoundaryIndent(sequenceIndentWidth: Int) throws {
        guard indentWidth(cursor.current) == sequenceIndentWidth,
              try cursor.peek()?.kind.isBlockEntry == true
        else {
            return
        }
        _ = try expect("indent") { $0.isIndent }
    }

    mutating func parseBlockSequenceItem(
        after entry: PureYAML.Parsing.Token,
        endMark: inout PureYAML.Parsing.Mark,
        allowMappingKeyTerminator: Bool,
    ) throws {
        if hasNodeOnSameLine(after: entry) {
            let properties = try consumeProperties()
            if cursor.current?.kind.isIndent == true {
                _ = try expect("indent") { $0.isIndent }
                endMark = try parseNode(properties: properties).endMark
                _ = try expect("dedent") { $0.isDedent }
                return
            }
            // After consuming anchor/tag properties the only content remaining on
            // this entry's line may be gone: a `mappingKey` or sibling `-` now on
            // the same line opens a nested collection, but one on a later line is
            // the next sibling, leaving this entry an empty scalar that carries
            // the properties.
            if cursor.current?.kind.isMappingKey == true, hasNodeOnSameLine(after: entry) {
                endMark = try parseBlockMapping(
                    properties: properties,
                    includeIndentedContinuation: true,
                    minimumColumn: entry.mark.column + 1,
                ).endMark
            } else if cursor.current?.kind.isBlockEntry == true, hasNodeOnSameLine(after: entry) {
                endMark = try parseBlockSequence(
                    properties: properties,
                    allowMappingKeyTerminator: allowMappingKeyTerminator,
                ).endMark
            } else if canBeginNode(cursor.current), hasNodeOnSameLine(after: entry) {
                endMark = try parseNode(properties: properties).endMark
            } else {
                let mark = properties.mark ?? entry.endMark
                try emitEmptyScalar(properties: properties, mark: mark)
                endMark = mark
            }
        } else if cursor.current?.kind.isIndent == true {
            _ = try expect("indent") { $0.isIndent }
            endMark = try parseNode().endMark
            _ = try expect("dedent") { $0.isDedent }
        } else {
            let mark = entry.endMark
            try emit(.scalar(value: "", anchor: nil, tag: nil, style: .plain, mark: mark))
            endMark = mark
        }
    }

    mutating func parseBlockMapping(
        properties: PureYAML.Parsing.NodeProperties,
        includeIndentedContinuation: Bool,
        minimumColumn: Int? = nil,
    ) throws -> PureYAML.Parsing.NodeResult {
        let startMark = properties.mark ?? cursor.current?.mark ?? .start
        let tokenColumn = cursor.current?.mark.column ?? startMark.column
        let contentColumn = min(startMark.column, tokenColumn)
        let boundaryColumn = minimumColumn ?? contentColumn
        var endMark = startMark
        try emit(.mappingStart(
            anchor: properties.anchor,
            tag: properties.tag,
            style: .block,
            mark: startMark,
        ))

        try parseBlockMappingPairs(
            boundaryColumn: boundaryColumn,
            includeIndentedContinuation: includeIndentedContinuation,
            endMark: &endMark,
        )
        if let current = cursor.current, !canEndBlockMapping(at: current, minimumColumn: boundaryColumn) {
            throw PureYAML.Parsing.ParseError.unexpectedToken(
                expected: "mapping key",
                actual: current.kind.description,
                line: current.mark.line,
                column: current.mark.column,
            )
        }
        try emit(.mappingEnd(mark: endMark))
        return PureYAML.Parsing.NodeResult(kind: .mapping, endMark: endMark)
    }

    mutating func parseBlockMappingPairs(
        boundaryColumn: Int,
        includeIndentedContinuation: Bool,
        endMark: inout PureYAML.Parsing.Mark,
    ) throws {
        while canContinueBlockMapping(minimumColumn: boundaryColumn) {
            endMark = try parseMappingPairAndBoundaries(
                boundaryColumn: boundaryColumn,
                includeIndentedContinuation: includeIndentedContinuation,
            ).endMark
        }
        while includeIndentedContinuation, cursor.current?.kind.isIndent == true {
            endMark = try parseIndentedBlockMappingPairs(boundaryColumn: boundaryColumn).endMark
        }
    }

    mutating func parseIndentedBlockMappingPairs(
        boundaryColumn: Int,
    ) throws -> PureYAML.Parsing.NodeResult {
        _ = try expect("indent") { $0.isIndent }
        guard cursor.current?.kind.isMappingKey == true else {
            throw unexpectedToken(expected: "mapping key")
        }
        var endMark = cursor.current?.mark ?? .start
        while canContinueBlockMapping(minimumColumn: boundaryColumn) {
            endMark = try parseMappingPairAndBoundaries(
                boundaryColumn: boundaryColumn,
                includeIndentedContinuation: true,
            ).endMark
        }
        if !canEndBlockMapping(at: cursor.current, minimumColumn: boundaryColumn) {
            _ = try expect("dedent") { $0.isDedent }
        }
        return PureYAML.Parsing.NodeResult(kind: .mapping, endMark: endMark)
    }

    mutating func parseMappingPairAndBoundaries(
        boundaryColumn: Int,
        includeIndentedContinuation: Bool,
    ) throws -> PureYAML.Parsing.NodeResult {
        let result = try parseMappingPair()
        try consumeMappingSiblingBoundaryDedents(minimumColumn: boundaryColumn)
        try consumeMappingSiblingBoundaryReindent(minimumColumn: boundaryColumn)
        if includeIndentedContinuation {
            try consumeDedents(atOrAbove: boundaryColumn)
            try consumeMappingSiblingBoundaryDedents(minimumColumn: boundaryColumn)
            try consumeMappingSiblingBoundaryReindent(minimumColumn: boundaryColumn)
        }
        return result
    }

    mutating func parseBlockScalar(
        properties: PureYAML.Parsing.NodeProperties,
    ) throws -> PureYAML.Parsing.NodeResult {
        let header = try expect("block scalar header") { kind in
            if case .blockScalarHeader = kind {
                return true
            }
            return false
        }
        guard case let .blockScalarHeader(_, _, value) = header.kind else {
            throw unexpectedToken(expected: "block scalar header")
        }
        let mark = properties.mark ?? header.mark
        try emit(.scalar(
            value: value,
            anchor: properties.anchor,
            tag: properties.tag,
            style: scalarStyle(for: header.kind),
            mark: mark,
        ))
        return PureYAML.Parsing.NodeResult(kind: .scalar, endMark: header.endMark)
    }

    func scalarStyle(for kind: PureYAML.Parsing.TokenKind) -> PureYAML.Parsing.ScalarStyle {
        switch kind {
        case .blockScalarHeader(.folded, _, _):
            .folded
        case .blockScalarHeader(.literal, _, _):
            .literal
        default:
            .plain
        }
    }
}