fileDB.go

package valuator

import (
	"bytes"
	"errors"
	"io"
	"io/ioutil"
	"log"
	"os"
)

/*
	FileDB is an internally supported implementation of the Database interface.
	This be used by applications that want to simply uses text files to save the
	output received from the valuator to store information for later use.
	The file path will be provided by the app and the name of the files will
	be detrmined by the ticker that is being queried.
*/

type fileDB struct {
	path   string
	writer map[string]*os.File
}

func newFileDB(url string) *fileDB {
	return &fileDB{
		path:   url,
		writer: make(map[string]*os.File),
	}
}

func (f *fileDB) generateFilePath(filename string) string {
	return f.path + filename + ".json"
}

func (f *fileDB) Open() error {
	_, err := os.Stat(f.path)
	return err
}

func (f *fileDB) Close() {
	for _, writer := range f.writer {
		writer.Close()
	}
}

func (f *fileDB) Read(filename string) (io.Reader, error) {
	file := f.generateFilePath(filename)
	fd, err := os.OpenFile(file, os.O_RDONLY, 0644)
	if err != nil {
		log.Println("Cannot open file ", file)
		return nil, errors.New("No data available at " + file)
	}
	data, err := ioutil.ReadAll(fd)
	if err != nil {
		log.Println("Error reading file ", file)
		return nil, errors.New("Error reading file " + file)
	}
	reader := bytes.NewReader(data)
	fd.Close()
	return reader, nil
}

func (f *fileDB) Write(ticker string, data []byte) error {
	if _, ok := f.writer[ticker]; !ok {
		file := f.generateFilePath(ticker)
		fd, err := os.OpenFile(file, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0644)
		if err != nil {
			log.Println("Cannot open file ", file)
			return errors.New("Cannot open file for write " + file)
		}
		f.writer[ticker] = fd
	}
	f.writer[ticker].Write(data)
	return nil
}