entry.go

package servicebindings

import (
	"bytes"
	"io"
	"os"
)

// Entry represents the read-only content of a binding entry.
type Entry struct {
	path  string
	file  *os.File
	value *bytes.Reader
}

// NewEntry returns a new Entry whose content is given by the file at the provided path.
func NewEntry(path string) *Entry {
	return &Entry{
		path: path,
	}
}

// NewWithValue returns a new Entry with predefined value.
func NewWithValue(value []byte) *Entry {
	return &Entry{
		value: bytes.NewReader(value),
	}
}

// ReadBytes reads the entire raw content of the entry. There is no need to call Close after calling ReadBytes.
func (e *Entry) ReadBytes() ([]byte, error) {
	if e.value != nil {
		return io.ReadAll(e.value)
	}
	return os.ReadFile(e.path)
}

// ReadString reads the entire content of the entry as a string. There is no need to call Close after calling
// ReadString.
func (e *Entry) ReadString() (string, error) {
	var bytes []byte
	var err error

	if e.value != nil {
		bytes, err = io.ReadAll(e.value)
		if err != nil {
			return "", err
		}
	} else {
		bytes, err = e.ReadBytes()
		if err != nil {
			return "", err
		}
	}

	return string(bytes), nil
}

// Read reads up to len(b) bytes from the entry. It returns the number of bytes read and any error encountered. At end
// of entry data, Read returns 0, io.EOF.
// Close must be called when all read operations are complete.
func (e *Entry) Read(b []byte) (int, error) {
	if e.value != nil {
		return e.value.Read(b)
	}

	if e.file == nil {
		file, err := os.Open(e.path)
		if err != nil {
			return 0, err
		}
		e.file = file
	}
	return e.file.Read(b)
}

// Close closes the entry and resets it for reading. After calling Close, any subsequent calls to Read will read entry
// data from the beginning. Close may be called on a closed entry without error.
func (e *Entry) Close() error {
	defer func() {
		e.file = nil
	}()

	if e.value != nil {
		_, err := e.value.Seek(0, io.SeekStart)
		return err
	} else if e.file == nil {
		return nil
	} else {
		return e.file.Close()
	}
}