package inspurlegacy

import (
	"regexp"
	"strconv"
	"strings"
	"time"

	"git.mchus.pro/mchus/logpile/internal/models"
)

// amiSyslogRe matches "<pri>  <ISO8601> host proc[pid]:  message".
var amiSyslogRe = regexp.MustCompile(`^<(\d+)>\s*(\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\S*)\s+(\S+)\s+(\S+?):\s*(.*)$`)

// ParseAMISyslog parses a flat AMI BMC severity log (err.log, warning.log, ...).
func ParseAMISyslog(content []byte, source string) []models.Event {
	var events []models.Event
	lineNo := 0
	for _, line := range strings.Split(string(content), "\n") {
		lineNo++
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		m := amiSyslogRe.FindStringSubmatch(line)
		if m == nil {
			continue
		}
		pri, err := strconv.Atoi(m[1])
		if err != nil {
			continue
		}
		ts, err := parseSyslogTime(m[2])
		if err != nil {
			continue
		}
		proc := m[4]
		msg := strings.TrimSpace(m[5])
		// AMI BMC pre-NTP lines carry a fabricated 1970 wall clock; without a
		// trustworthy boot epoch they cannot become dated events.
		if bogusYear(ts) {
			continue
		}

		severity := syslogSeverity(pri, source)
		if isBenignSyslogMessage(msg) {
			severity = models.SeverityInfo
		}

		events = append(events, models.Event{
			ID:          strings.TrimSuffix(source, ".log") + "_" + itoa(lineNo),
			Timestamp:   ts,
			Source:      "syslog/" + strings.TrimSuffix(source, ".log"),
			SensorType:  "syslog",
			SensorName:  proc,
			Severity:    severity,
			Description: msg,
			RawData:     line,
		})
	}
	return events
}

func parseSyslogTime(s string) (time.Time, error) {
	if t, err := time.Parse(time.RFC3339, s); err == nil {
		return t, nil
	}
	return time.Parse("2006-01-02T15:04:05.999999-07:00", s)
}

// benignSyslogSubstrings are driver banners and inventory-provisioning notices
// that AMI routes to alert.log/warning.log despite describing no fault. The PRI
// value is not trustworthy for this observed set.
var benignSyslogSubstrings = []string{
	"helper module driver version",
	"copyright (c)",
	"changed from null to",
	"sn changed from",
	"color depth is",
}

func isBenignSyslogMessage(msg string) bool {
	low := strings.ToLower(msg)
	for _, s := range benignSyslogSubstrings {
		if strings.Contains(low, s) {
			return true
		}
	}
	return false
}

// syslogSeverity derives severity from the RFC 5424 PRI low three bits, falling
// back to the source filename.
func syslogSeverity(pri int, source string) models.Severity {
	switch pri & 7 {
	case 0, 1, 2:
		return models.SeverityCritical
	case 3, 4:
		return models.SeverityWarning
	case 5, 6, 7:
		return models.SeverityInfo
	}
	return severityFromSource(source)
}

func severityFromSource(source string) models.Severity {
	low := strings.ToLower(source)
	switch {
	case strings.Contains(low, "emerg"), strings.Contains(low, "alert"), strings.Contains(low, "crit"):
		return models.SeverityCritical
	case strings.Contains(low, "err"), strings.Contains(low, "warn"):
		return models.SeverityWarning
	default:
		return models.SeverityInfo
	}
}