@testable import PureXML
import Testing

@Suite("XSLT xsl:decimal-format")
struct XSLTDecimalFormatTests {
    private let xsl = "xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\""

    private func transform(_ stylesheet: String, _ source: String) throws -> String {
        try PureXML.XSLT.transform(stylesheet: stylesheet, source: source)
    }

    private func formatNumber(_ select: String, decimalFormats: String = "") -> String {
        """
        <xsl:stylesheet version="1.0" \(xsl)>
          <xsl:output method="text"/>
          \(decimalFormats)
          <xsl:template match="/"><xsl:value-of select="\(select)"/></xsl:template>
        </xsl:stylesheet>
        """
    }

    @Test("The default format still works")
    func test_default() throws {
        #expect(try transform(formatNumber("format-number(1234.5, '#,##0.00')"), "<x/>") == "1,234.50")
    }

    @Test("A named European format swaps the decimal and grouping separators")
    func test_european() throws {
        let style = formatNumber(
            "format-number(1234.5, '#.##0,00', 'eu')",
            decimalFormats: "<xsl:decimal-format name=\"eu\" decimal-separator=\",\" grouping-separator=\".\"/>",
        )
        #expect(try transform(style, "<x/>") == "1.234,50")
    }

    @Test("A custom percent and minus sign are honored")
    func test_percentMinus() throws {
        let style = formatNumber(
            "format-number(-0.25, '0%', 'p')",
            decimalFormats: "<xsl:decimal-format name=\"p\" minus-sign=\"!\"/>",
        )
        #expect(try transform(style, "<x/>") == "!25%")
    }

    @Test("A custom NaN string is used for non-numbers")
    func test_nan() throws {
        let style = formatNumber(
            "format-number(number('abc'), '0', 'n')",
            decimalFormats: "<xsl:decimal-format name=\"n\" NaN=\"not-a-number\"/>",
        )
        #expect(try transform(style, "<x/>") == "not-a-number")
    }

    @Test("The unnamed decimal-format overrides the global default")
    func test_unnamedDefault() throws {
        let style = formatNumber(
            "format-number(5, '0')",
            decimalFormats: "<xsl:decimal-format zero-digit=\"0\" minus-sign=\"~\"/>",
        )
        // 5 formats plainly; a negative shows the overridden minus sign.
        #expect(try transform(style, "<x/>") == "5")
        let neg = formatNumber("format-number(-5, '0')", decimalFormats: "<xsl:decimal-format minus-sign=\"~\"/>")
        #expect(try transform(neg, "<x/>") == "~5")
    }
}