// Copyright 2026 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// A stand-alone Go module that generates ../schema.go using the
// upstream Wycheproof JSON schema documents.
//
// We maintain this in a separate Go module and vendor the resulting
// generated .go code to avoid the standard library taking a direct
// dependency on the c2sp/wycheproof or atombender/go-jsonschema modules.

package main

import (
	"bufio"
	"fmt"
	"io/fs"
	"log"
	"os"
	"path/filepath"
	"strings"

	"github.com/atombender/go-jsonschema/pkg/generator"
	"github.com/c2sp/wycheproof"
)

func main() {
	ouputName := "schema.go"
	cfg := generator.Config{
		DefaultPackageName: "wycheproof",
		DefaultOutputName:  ouputName,
		Tags:               []string{"json"},
		Warner: func(message string) {
			log.Printf("go-jsonschema: %s", message)
		},
	}
	gen, err := generator.New(cfg)
	if err != nil {
		log.Fatal(err)
	}

	// Without upstream modifications we can't use the embedded Wycheproof
	// schema FS directly w/ go-jsonschema and instead make files in a tempdir
	// on the native FS. See https://github.com/omissis/go-jsonschema/issues/495
	schemaDir, err := os.MkdirTemp("", "*-wycheproof")
	if err != nil {
		log.Fatal(err)
	}
	defer os.RemoveAll(schemaDir)

	rawSchemas, _ := fs.ReadDir(wycheproof.Schemas, ".")
	for _, entry := range rawSchemas {
		entryName := entry.Name()
		schemaFile := filepath.Join(schemaDir, entryName)

		schemaData, err := fs.ReadFile(wycheproof.Schemas, entryName)
		if err != nil {
			log.Fatalf("reading %s: %v", entryName, err)
		}
		err = os.WriteFile(schemaFile, schemaData, 0644)
		if err != nil {
			log.Fatalf("writing %s: %v", schemaFile, err)
		}
	}

	// Note: it's important we process schemas in a second pass after writing
	// **all** of the schema file content to disk so that go-jsonschema can
	// resolve cross-file references.
	for _, entry := range rawSchemas {
		entryName := entry.Name()
		schemaFile := filepath.Join(schemaDir, entryName)

		err = gen.DoFile(schemaFile)
		if err != nil {
			log.Fatalf("processing %s: %v", schemaFile, err)
		}
	}

	sources, err := gen.Sources()
	if err != nil {
		log.Fatalf("error generating sources: %v\n", err)
	}
	if sourceCount := len(sources); sourceCount != 1 {
		log.Fatalf("expected to generate 1 source file, got %d\n", sourceCount)
	}
	content, ok := sources[ouputName]
	if !ok {
		log.Fatalf("missing generated %q output file source", ouputName)
	}
	outFile := filepath.Join("../", ouputName)
	if err := os.WriteFile(outFile, content, 0644); err != nil {
		log.Fatalf("error writing file %s: %v\n", outFile, err)
	}

	// Write a sibling file recording the Wycheproof module version that the
	// generated schema.go was produced against. The wycheproof package uses
	// this constant to fetch matching test vectors at runtime. We avoid reading
	// go.sum at test time because it might not be available (e.g. if the test
	// binary was copied to a remote machine).
	version, err := wycheproofVersionFromSum("go.sum")
	if err != nil {
		log.Fatalf("extracting wycheproof version: %v", err)
	}
	const versionFile = "../schemaversion.go"
	versionSrc := fmt.Sprintf(`// Copyright 2026 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Code generated by _schema/schema_gen.go, DO NOT EDIT.

package wycheproof

// wycheproofVersion is the github.com/c2sp/wycheproof module version that
// schema.go was generated against.
const wycheproofVersion = %q
`, version)
	if err := os.WriteFile(versionFile, []byte(versionSrc), 0644); err != nil {
		log.Fatalf("writing %s: %v", versionFile, err)
	}
}

// wycheproofVersionFromSum returns the github.com/c2sp/wycheproof module
// version recorded in the given go.sum file.
func wycheproofVersionFromSum(path string) (string, error) {
	f, err := os.Open(path)
	if err != nil {
		return "", err
	}
	defer f.Close()

	var version string
	found := 0
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		fields := strings.Fields(scanner.Text())
		if len(fields) == 3 && fields[0] == "github.com/c2sp/wycheproof" {
			version = strings.TrimSuffix(fields[1], "/go.mod")
			found++
		}
	}
	if err := scanner.Err(); err != nil {
		return "", err
	}
	switch {
	case found == 0:
		return "", fmt.Errorf("%s: missing github.com/c2sp/wycheproof entry", path)
	case found > 2:
		return "", fmt.Errorf("%s: %d github.com/c2sp/wycheproof entries (run 'go mod tidy')", path, found)
	}
	return version, nil
}