package collector

import (
	"strings"

	"git.tornberg.me/go-otel/internal/issues"
	"go.opentelemetry.io/collector/pdata/pcommon"
	"go.opentelemetry.io/collector/pdata/plog"
	"go.opentelemetry.io/collector/pdata/ptrace"
)

// maxIssueTitleLen bounds how much of a log body is kept as an issue title,
// so a single noisy log line can't blow up issue payload size.
const maxIssueTitleLen = 200

// extractSpanErrors scans traces for spans with an error status and records
// one issue occurrence per error found.
func extractSpanErrors(tracker *issues.Tracker, td ptrace.Traces, timestamp int64) {
	resourceSpans := td.ResourceSpans()
	for i := 0; i < resourceSpans.Len(); i++ {
		rs := resourceSpans.At(i)
		service := resourceServiceName(rs.Resource())

		scopeSpans := rs.ScopeSpans()
		for j := 0; j < scopeSpans.Len(); j++ {
			spans := scopeSpans.At(j).Spans()
			for k := 0; k < spans.Len(); k++ {
				span := spans.At(k)
				if span.Status().Code() != ptrace.StatusCodeError {
					continue
				}

				title := spanErrorTitle(span)
				tracker.Record("span_error", service, title, issues.Sample{
					Timestamp: timestamp,
					TraceID:   idString(span.TraceID()),
					SpanID:    idString(span.SpanID()),
					Message:   title,
				})
			}
		}
	}
}

// extractLogErrors scans logs for error/fatal severity records and records
// one issue occurrence per error found.
func extractLogErrors(tracker *issues.Tracker, ld plog.Logs, timestamp int64) {
	resourceLogs := ld.ResourceLogs()
	for i := 0; i < resourceLogs.Len(); i++ {
		rl := resourceLogs.At(i)
		service := resourceServiceName(rl.Resource())

		scopeLogs := rl.ScopeLogs()
		for j := 0; j < scopeLogs.Len(); j++ {
			records := scopeLogs.At(j).LogRecords()
			for k := 0; k < records.Len(); k++ {
				record := records.At(k)
				if !isErrorLog(record) {
					continue
				}

				title := logErrorTitle(record)
				tracker.Record("log_error", service, title, issues.Sample{
					Timestamp: timestamp,
					TraceID:   idString(record.TraceID()),
					SpanID:    idString(record.SpanID()),
					Message:   title,
				})
			}
		}
	}
}

func isErrorLog(record plog.LogRecord) bool {
	if record.SeverityNumber() >= plog.SeverityNumberError {
		return true
	}
	switch strings.ToUpper(strings.TrimSpace(record.SeverityText())) {
	case "ERROR", "FATAL", "CRITICAL":
		return true
	default:
		return false
	}
}

func spanErrorTitle(span ptrace.Span) string {
	events := span.Events()
	for i := 0; i < events.Len(); i++ {
		event := events.At(i)
		if event.Name() != "exception" {
			continue
		}
		excType := attrString(event.Attributes(), "exception.type")
		excMsg := attrString(event.Attributes(), "exception.message")
		switch {
		case excType != "" && excMsg != "":
			return excType + ": " + excMsg
		case excMsg != "":
			return excMsg
		case excType != "":
			return excType
		}
	}

	if msg := span.Status().Message(); msg != "" {
		return span.Name() + ": " + msg
	}
	return span.Name() + " (error)"
}

func logErrorTitle(record plog.LogRecord) string {
	excType := attrString(record.Attributes(), "exception.type")
	excMsg := attrString(record.Attributes(), "exception.message")
	switch {
	case excType != "" && excMsg != "":
		return truncate(excType + ": " + excMsg)
	case excMsg != "":
		return truncate(excMsg)
	}

	body := strings.TrimSpace(record.Body().AsString())
	if body == "" {
		return "log error"
	}
	return truncate(body)
}

func truncate(s string) string {
	if len(s) <= maxIssueTitleLen {
		return s
	}
	return s[:maxIssueTitleLen] + "…"
}

func resourceServiceName(res pcommon.Resource) string {
	if name := attrString(res.Attributes(), "service.name"); name != "" {
		return name
	}
	return "unknown"
}

// attrString safely reads a string attribute, since a Value obtained from a
// missing Map key is not valid to call methods on.
func attrString(attrs pcommon.Map, key string) string {
	if v, ok := attrs.Get(key); ok {
		return v.AsString()
	}
	return ""
}

type traceOrSpanID interface {
	IsEmpty() bool
	String() string
}

func idString(id traceOrSpanID) string {
	if id.IsEmpty() {
		return ""
	}
	return id.String()
}