package parser

import (
	"fmt"
	"regexp"
	"strconv"
	"time"
)

// AccessEntry holds a parsed nginx combined-format access log entry.
type AccessEntry struct {
	RemoteAddr string
	RemoteUser string
	Time       time.Time
	Method     string
	Path       string
	Protocol   string
	Status     int
	BytesSent  int64
	Referer    string
	UserAgent  string
}

// accessLogRe matches nginx combined log format.
// Groups: remoteAddr, remoteUser, time, method, path, protocol, status, bytes, referer, userAgent
var accessLogRe = regexp.MustCompile(
	`^(\S+) - (\S+) \[([^\]]+)\] "(\S+) (\S+) (\S+)" (\d+) (\d+|-) "([^"]*)" "([^"]*)"$`,
)

const accessTimeLayout = "02/Jan/2006:15:04:05 -0700"

// ParseAccessLine parses a single nginx access log line.
// Returns an error for malformed lines.
func ParseAccessLine(line string) (AccessEntry, error) {
	m := accessLogRe.FindStringSubmatch(line)
	if m == nil {
		return AccessEntry{}, fmt.Errorf("access: no match: %q", line)
	}

	t, err := time.Parse(accessTimeLayout, m[3])
	if err != nil {
		return AccessEntry{}, fmt.Errorf("access: parse time %q: %w", m[3], err)
	}

	status, err := strconv.Atoi(m[7])
	if err != nil {
		return AccessEntry{}, fmt.Errorf("access: parse status %q: %w", m[7], err)
	}

	var bytes int64
	if m[8] != "-" {
		bytes, err = strconv.ParseInt(m[8], 10, 64)
		if err != nil {
			return AccessEntry{}, fmt.Errorf("access: parse bytes %q: %w", m[8], err)
		}
	}

	return AccessEntry{
		RemoteAddr: m[1],
		RemoteUser: m[2],
		Time:       t,
		Method:     m[4],
		Path:       m[5],
		Protocol:   m[6],
		Status:     status,
		BytesSent:  bytes,
		Referer:    m[9],
		UserAgent:  m[10],
	}, nil
}