package generator

/*
Package generator provides functionality for generating a source file containing
DEPS entries. It is designed to require the absolute minimum of boilerplate from
the caller so that they just need to call MustGenerate, along with the necessary
go:build / +build comments:

```
	generator.MustGenerate("../../../DEPS")
```
*/

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"go.skia.org/infra/go/depot_tools/deps_parser"
	"go.skia.org/infra/go/skerr"
	"go.skia.org/infra/go/sklog"
)

const (
	targetFile = "deps_gen.go"
	header     = `// Code generated by "go run generate.go"; DO NOT EDIT

package deps

import (
	"go.skia.org/infra/go/depot_tools/deps_parser"
)

var deps = deps_parser.DepsEntries{`

	entryTmpl = `	"%s": {
		Id:      "%s",
		Version: "%s",
		Path:    "%s",
	},`
	footer = `}
`
)

// Generate creates a deps_gen.go file with the contents of the DEPS file.
// It assumes that it's being run via "go generate" and therefore the output
// file is to be written to the current working directory. relPathToDeps is the
// relative path to the DEPS file from the current working directory.
func Generate(relPathToDeps string) error {
	cwd, err := os.Getwd()
	if err != nil {
		return skerr.Wrap(err)
	}
	depsPath := filepath.Join(cwd, filepath.FromSlash(relPathToDeps))
	depsContents, err := os.ReadFile(depsPath)
	if err != nil {
		return skerr.Wrap(err)
	}
	entries, err := deps_parser.ParseDeps(string(depsContents))
	if err != nil {
		return skerr.Wrap(err)
	}
	ids := make([]string, 0, len(entries))
	for id := range entries {
		ids = append(ids, id)
	}
	sort.Strings(ids)

	parts := []string{header}
	for _, id := range ids {
		entry := entries[id]
		parts = append(parts, fmt.Sprintf(entryTmpl, entry.Id, entry.Id, entry.Version, entry.Path))
	}
	parts = append(parts, footer)

	targetContents := strings.Join(parts, "\n")
	if err := os.WriteFile(targetFile, []byte(targetContents), os.ModePerm); err != nil {
		return skerr.Wrap(err)
	}
	return nil
}

// MustGenerate runs Generate and panics if it fails.
func MustGenerate(relPathToDeps string) {
	if err := Generate(relPathToDeps); err != nil {
		sklog.Fatal(err)
	}
}