package supervisor

import (
	"bufio"
	"bytes"
	"encoding/json"
	"io"
	"io/ioutil"
	"strings"
)

// MakeJsonLineParser is called with an io.Reader, and returns a function, that when called will output references to
// map[string]interface{} objects that contain the parsed json data.
// If an invalid json is encountered, all the characters up until a new-line will be dropped.
func MakeJsonLineParser(fromR io.Reader, bufferSize int) ProduceFn {
	br := bufio.NewReaderSize(fromR, bufferSize)
	dec := json.NewDecoder(br)
	return func() (*interface{}, bool) {
		var v interface{}
		if err := dec.Decode(&v); err == nil {
			return &v, false
		} else if err != io.EOF {
			rest, _ := ioutil.ReadAll(dec.Buffered())
			restLines := bytes.SplitAfterN(rest, []byte{'\n'}, 2)
			if len(restLines) > 1 {
				// todo: test memory consumption on many mistakes (which will happen)
				dec = json.NewDecoder(io.MultiReader(bytes.NewReader(restLines[1]), br))
			} else {
				dec = json.NewDecoder(br)
			}
		}
		return nil, true
	}
}

// MakeLineParser is called with an io.Reader, and returns a function, that when called will output references to
// strings that contain the bytes read from the io.Reader (without the new-line suffix).
func MakeLineParser(fromR io.Reader, bufferSize int) ProduceFn {
	br := bufio.NewReaderSize(fromR, bufferSize)
	return func() (*interface{}, bool) {
		str, err := br.ReadString('\n')
		if err == nil {
			res := (interface{})(strings.TrimSuffix(str, string('\n')))
			return &res, false
		}
		return nil, err == io.EOF
	}
}

// MakeLineParser is called with an io.Reader, and returns a function, that when called will output references to
// byte slices that contain the bytes read from the io.Reader.
func MakeBytesParser(fromR io.Reader, bufferSize int) ProduceFn {
	br := bufio.NewReaderSize(fromR, bufferSize)
	return func() (*interface{}, bool) {
		v, err := br.ReadBytes('\n')
		if err == nil {
			res := (interface{})(bytes.TrimSuffix(v, []byte{'\n'}))
			return &res, false
		}
		return nil, err == io.EOF
	}
}