// Copyright 2017 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.

package maintner

import (
	"bytes"
	"compress/gzip"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"github.com/golang/protobuf/proto"
	"golang.org/x/build/maintner/maintpb"
)

// A MutationLogger logs mutations.
type MutationLogger interface {
	Log(*maintpb.Mutation) error
}

// DiskMutationLogger logs mutations to disk.
type DiskMutationLogger struct {
	directory string
}

// NewDiskMutationLogger creates a new DiskMutationLogger, which will create
// mutations in the given directory.
func NewDiskMutationLogger(directory string) *DiskMutationLogger {
	return &DiskMutationLogger{directory: directory}
}

func (d *DiskMutationLogger) filename() string {
	now := time.Now().UTC()
	return filepath.Join(d.directory, fmt.Sprintf("maintner-%s.proto.gz", now.Format("2006-01-02")))
}

// Log will write m to disk. If a mutation file does not exist for the current
// day, it will be created.
func (d *DiskMutationLogger) Log(m *maintpb.Mutation) error {
	f, err := os.OpenFile(d.filename(), os.O_RDWR|os.O_APPEND|os.O_CREATE, 0600)
	if err != nil {
		return err
	}
	data, err := proto.Marshal(m)
	if err != nil {
		return err
	}
	var buf bytes.Buffer
	zw := gzip.NewWriter(&buf)
	if _, err := zw.Write(data); err != nil {
		return err
	}
	if err := zw.Close(); err != nil {
		return err
	}
	if _, err := f.Write(buf.Bytes()); err != nil {
		return err
	}
	return f.Close()
}