// SPDX-License-Identifier: MIT

//go:build ignore

// Command fold reads the "XXXX YYYY" lines printed by `runner.dll --fold`
// (see gen/runner) on stdin and writes fold_tables.go: the case folding of
// .NET's StringComparison.OrdinalIgnoreCase, code point by code point.
package main

import (
	"bufio"
	"flag"
	"fmt"
	"go/format"
	"os"
	"strconv"
	"strings"
)

func main() {
	out := flag.String("o", "", "output file (default stdout)")
	flag.Parse()
	var b strings.Builder
	b.WriteString("// SPDX-License-Identifier: MIT\n\n// Code generated by gen/fold.go from `runner.dll --fold` (gen/runner); DO NOT EDIT.\n\npackage expr\n\n")
	b.WriteString("// ordinalUpper maps a code point to the one that .NET's OrdinalIgnoreCase comparison treats\n// it as, sorted by the first element. Code points that are not listed stand for themselves.\n")
	b.WriteString("var ordinalUpper = [...][2]rune{\n")
	sc := bufio.NewScanner(os.Stdin)
	n := 0
	for sc.Scan() {
		f := strings.Fields(sc.Text())
		if len(f) != 2 {
			continue
		}
		from, err1 := strconv.ParseInt(f[0], 16, 32)
		to, err2 := strconv.ParseInt(f[1], 16, 32)
		if err1 != nil || err2 != nil {
			fmt.Fprintln(os.Stderr, "bad line:", sc.Text())
			os.Exit(1)
		}
		fmt.Fprintf(&b, "\t{0x%04X, 0x%04X},\n", from, to)
		n++
	}
	b.WriteString("}\n")
	src, err := format.Source([]byte(b.String()))
	if err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
	if n == 0 {
		fmt.Fprintln(os.Stderr, "no input")
		os.Exit(1)
	}
	if *out == "" {
		os.Stdout.Write(src)
		return
	}
	if err := os.WriteFile(*out, src, 0o644); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}