/*
Copyright 2019 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

import (
	"bufio"
	"io"
	"regexp"
	"strings"
	"time"

	"k8s.io/klog/v2"
)

func processLines(reader io.Reader, regex *regexp.Regexp) ([]*logEntry, error) {
	var result []*logEntry
	r := bufio.NewReader(reader)
	for {
		line, err := r.ReadBytes('\n')
		if err != nil {
			if err != io.EOF {
				return nil, err
			}
			if len(line) == 0 {
				break
			}
		}
		matched, entry, err := processLine(line, regex)
		if err != nil {
			// TODO There is a problem that files finish with incomplete line
			klog.Errorf("%s error parsing line %s", err, line)
			continue
		}
		if matched {
			result = append(result, entry)
		}
	}
	return result, nil
}

func processLine(line []byte, regex *regexp.Regexp) (bool, *logEntry, error) {
	if !regex.Match(line) {
		return false, nil, nil
	}

	parsed, err := parseLine(string(line))
	return true, parsed, err
}

func parseLine(line string) (*logEntry, error) {
	const startMarker = "ReceivedTimestamp\":\""
	const endMarker = "\",\"stageTimestamp"
	start := strings.Index(line, startMarker)
	end := strings.Index(line, endMarker)
	if start == -1 {
		return &logEntry{}, &parseLineFailedError{line}
	}
	if end == -1 {
		return &logEntry{}, &parseLineFailedError{line}
	}
	timestamp := line[(start + len(startMarker)):end]
	parsed, e := time.Parse(time.RFC3339Nano, timestamp)
	if e != nil {
		return nil, e
	}
	return &logEntry{log: line, time: parsed}, nil
}

func (e *parseLineFailedError) Error() string {
	return "Failed to parse line: " + e.line
}

type parseLineFailedError struct {
	line string
}

type logEntry struct {
	log  string
	time time.Time
}
