package gateway

import (
	"net/http"
	"strconv"
	"time"

	apperr "git.yeij.top/AskaEth/Cyrene_v2/internal/errors"
	"git.yeij.top/AskaEth/Cyrene_v2/internal/runtime/trace"
)

// Default list limits shared by the trace/audit endpoints. Compile-time constants
// so no magic number appears in the run path (project rule §10).
const (
	defaultObsLimit = 50
	maxObsLimit     = 500
)

// observability bundles the gateway's live admin instrumentation: the request
// metrics counter, the trace span ring buffer and the audit store. It is built in
// New and is safe for concurrent use.
type observability struct {
	metrics  *MetricsCollector
	traceBuf *RingBuffer
	audit    AuditStore
}

// newObservability builds the instrumentation, falling back to an in-memory audit
// store when no store is injected.
func newObservability(deps Deps) *observability {
	obs := &observability{
		metrics:  newMetricsCollector(),
		traceBuf: newRingBuffer(defaultTraceBufCap),
	}
	if deps.AuditStore != nil {
		obs.audit = deps.AuditStore
	} else {
		obs.audit = newMemoryAuditStore()
	}
	return obs
}

// ObserveSpan feeds a completed trace span into the gateway's ring buffer and the
// LLM/subagent metric counters. It is the gateway's trace injection point: the
// composition root wires the loop tracer here (e.g. through TraceSink) so the
// admin panel can query spans without the gateway touching wire.go.
func (s *Server) ObserveSpan(rec trace.SpanRecord) {
	if s.obs == nil {
		return
	}
	s.obs.traceBuf.Append(rec)
	s.obs.metrics.Observe(rec)
}

// TraceSink returns a trace.Writer that appends completed spans to the gateway's
// trace ring buffer. Combine it with the existing JSONRecorder in the composition
// root (e.g. trace.New(MultiTraceWriter{...})) so spans both hit stderr and the
// admin panel.
func (s *Server) TraceSink() trace.Writer {
	if s.obs == nil {
		return nil
	}
	return traceSink{s.obs.traceBuf}
}

// recordMetric counts one request for the observability panel.
func (s *Server) recordMetric(method, path string, status int, durMs int64) {
	if s.obs == nil {
		return
	}
	s.obs.metrics.Record(method, path, status, durMs)
}

// adminObservabilityMetrics returns the current gateway metrics (admin read).
func (s *Server) adminObservabilityMetrics(w http.ResponseWriter, r *http.Request) {
	if s.obs == nil {
		writeJSON(w, http.StatusOK, AdminMetrics{
			PerMethod: map[string]int64{}, PerPath: map[string]int64{}, StatusCounts: map[string]int64{},
		})
		return
	}
	writeJSON(w, http.StatusOK, s.obs.metrics.Snapshot(time.Now()))
}

// adminObservabilityTrace returns the most recent traced spans (admin read).
func (s *Server) adminObservabilityTrace(w http.ResponseWriter, r *http.Request) {
	if s.obs == nil {
		writeJSON(w, http.StatusOK, []AdminTraceSpan{})
		return
	}
	spans := s.obs.traceBuf.Snapshot(parseLimit(r))
	out := make([]AdminTraceSpan, 0, len(spans))
	for _, sp := range spans {
		out = append(out, adminSpanOf(sp))
	}
	writeJSON(w, http.StatusOK, out)
}

// adminObservabilityAudit returns the most recent audit entries (admin read).
func (s *Server) adminObservabilityAudit(w http.ResponseWriter, r *http.Request) {
	if s.obs == nil || s.obs.audit == nil {
		writeJSON(w, http.StatusOK, []AuditRecord{})
		return
	}
	records, err := s.obs.audit.List(r.Context(), parseLimit(r))
	if err != nil {
		s.log.Error("list audit", "err", err)
		writeError(w, apperr.Wrap(apperr.ErrInternal, "audit_failed", "failed to list audit records"))
		return
	}
	writeJSON(w, http.StatusOK, records)
}

// parseLimit parses the ?limit= query param, clamping to [1, maxObsLimit], and
// selects defaultObsLimit when absent or invalid.
func parseLimit(r *http.Request) int {
	n, err := strconv.Atoi(r.URL.Query().Get("limit"))
	if err != nil || n <= 0 {
		return defaultObsLimit
	}
	if n > maxObsLimit {
		return maxObsLimit
	}
	return n
}