// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Command make_builtin_vdlroot runs at jiri go generate time. It emits a Go
// source file called builtin_vdlroot.go containing a gzip'd version of all the
// core VDL types required by the VDL tool. This allows the VDL tool to run
// 'standalone' (i.e. without access to the Vanadium source code).
//
// +build ignored

package main

import (
	"archive/tar"
	"compress/gzip"
	"encoding/base64"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strings"
)

const (
	outputPreamble = `// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file is automatically generated, your changes will be lost.
// See make_builtin_vdlroot.go.

package main

//go:generate jiri go run make_builtin_vdlroot.go

const (
	// builtinVdlrootData contains a base64-encoded gzip'd tar file. This file
	// contains all of the VDL files required to run the VDL tool.
	builtinVdlrootData = ` + "`"
	outputFooter = "`" + `
)
`
)

// writeBytes writes the given bytes to the given writer, returning an error if
// the underlying Write fails or if the number of bytes written is not equal to
// len(content).
func writeBytes(out io.Writer, content []byte) error {
	n, err := out.Write(content)
	if err == nil && n != len(content) {
		err = fmt.Errorf("wrote an unexpected number of bytes, wanted %d, wrote %d", len(content), n)
	}
	return err
}

// writeString writes the given string to the given writer, returning an error
// if the underlying Write fails or if the number of bytes written is not equal
// to len(content).
func writeString(out io.Writer, content string) error {
	return writeBytes(out, []byte(content))
}

type wrapWriter struct {
	writer       io.Writer
	totalWritten int
}

// Writes b to the underlying writer but inserts a \n every 78 characters. The
// returned bytes-written count includes the \n characters.
func (w *wrapWriter) Write(b []byte) (int, error) {
	const max = 78
	n := 0
	for len(b) > 0 {
		newline := true
		chunk := max - w.totalWritten%max
		if len(b) < chunk {
			chunk = len(b)
			newline = false
		}
		if err := writeBytes(w.writer, b[:chunk]); err != nil {
			return n, err
		}
		n += chunk
		w.totalWritten += chunk
		b = b[chunk:]
		if newline {
			if err := writeString(w.writer, "\n"); err != nil {
				return n, err
			}
			n++
		}
	}
	return n, nil
}

// writeVdlrootData creates a gzip'd tar file containing all of the VDL files
// in vdlroot. The data is encoded as base64. Does not close out.
func writeVdlrootData(out io.Writer) error {
	jiriRoot := os.Getenv("JIRI_ROOT")
	if jiriRoot == "" {
		return fmt.Errorf("JIRI_ROOT is not set")
	}
	srcDir := filepath.Join(jiriRoot, "release", "go", "src")
	vdlroot := filepath.Join(srcDir, "v.io", "v23", "vdlroot")
	wrapWriter := &wrapWriter{
		writer:       out,
		totalWritten: 0,
	}
	base64writer := base64.NewEncoder(base64.StdEncoding, wrapWriter)
	gzipWriter := gzip.NewWriter(base64writer)
	tarWriter := tar.NewWriter(gzipWriter)
	walkFn := func(path string, info os.FileInfo, err error) error {
		if strings.HasSuffix(path, ".vdl") {
			content, err := ioutil.ReadFile(path)
			if err != nil {
				return err
			}
			relPath, err := filepath.Rel(srcDir, path)
			if err != nil {
				return err
			}
			header := tar.Header{
				Mode: int64(0644),
				Name: relPath,
				Size: int64(len(content)),
			}
			if err := tarWriter.WriteHeader(&header); err != nil {
				return err
			}
			return writeBytes(tarWriter, content)
		}
		return nil
	}
	if err := filepath.Walk(vdlroot, walkFn); err != nil {
		log.Printf("Walk() failed: %v", err)
	}
	if err := tarWriter.Close(); err != nil {
		log.Printf("Close() of tar file failed: %v", err)
		return err
	}
	if err := gzipWriter.Close(); err != nil {
		log.Printf("Close() of gzip file failed: %v", err)
		return err
	}
	if err := base64writer.Close(); err != nil {
		log.Printf("Close() of base64 file failed: %v", err)
		return err
	}
	return nil
}

func main() {
	filename := "builtin_vdlroot.go"
	f, err := os.Create(filename)
	if err != nil {
		log.Printf("Create(%q) failed: %v", filename, err)
		os.Exit(1)
	}
	defer f.Close()
	if err := writeString(f, outputPreamble); err != nil {
		os.Exit(1)
	}
	if err := writeVdlrootData(f); err != nil {
		os.Exit(1)
	}
	if err := writeString(f, outputFooter); err != nil {
		os.Exit(1)
	}
}