package api

import (
	"encoding/json"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"time"
)

type passRateResponse struct {
	Skill    string   `json:"skill"`
	Window   string   `json:"window"`
	Pass     int      `json:"pass"`
	Fail     int      `json:"fail"`
	Skip     int      `json:"skip"`
	Total    int      `json:"total"`
	PassRate *float64 `json:"pass_rate"`
}

// PassRate handles GET /pass-rate?skill=X&window=Y.
// Walks brainDir/sessions/*.jsonl, filters by skill name and timestamp,
// returns aggregated counts and pass rate.
func (h *Handler) PassRate(w http.ResponseWriter, r *http.Request) {
	skill := r.URL.Query().Get("skill")
	if skill == "" {
		writeError(w, http.StatusBadRequest, "skill is required")
		return
	}

	windowStr := r.URL.Query().Get("window")
	if windowStr == "" {
		windowStr = "7d"
	}
	window, err := parseWindow(windowStr)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid window: "+err.Error())
		return
	}

	cutoff := time.Now().UTC().Add(-window)
	pass, fail, skip := 0, 0, 0

	sessionsDir := filepath.Join(h.brainDir, "sessions")
	entries, err := os.ReadDir(sessionsDir)
	if err != nil && !os.IsNotExist(err) {
		writeError(w, http.StatusInternalServerError, "read sessions dir: "+err.Error())
		return
	}

	for _, entry := range entries {
		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".jsonl") {
			continue
		}
		body, err := os.ReadFile(filepath.Join(sessionsDir, entry.Name()))
		if err != nil {
			continue // skip unreadable files
		}
		for _, line := range strings.Split(string(body), "\n") {
			line = strings.TrimSpace(line)
			if line == "" {
				continue
			}
			var rec struct {
				Timestamp   string `json:"timestamp"`
				Skill       string `json:"skill"`
				FinalStatus string `json:"final_status"`
			}
			if err := json.Unmarshal([]byte(line), &rec); err != nil {
				continue // malformed — skip
			}
			if rec.Skill != skill {
				continue
			}
			ts, err := time.Parse(time.RFC3339, rec.Timestamp)
			if err != nil {
				continue
			}
			if ts.Before(cutoff) {
				continue
			}
			switch normalizeStatus(rec.FinalStatus) {
			case "pass":
				pass++
			case "fail":
				fail++
			case "skip":
				skip++
			}
		}
	}

	total := pass + fail + skip
	resp := passRateResponse{
		Skill:  skill,
		Window: windowStr,
		Pass:   pass,
		Fail:   fail,
		Skip:   skip,
		Total:  total,
	}
	if pass+fail > 0 {
		rate := float64(pass) / float64(pass+fail)
		resp.PassRate = &rate
	}

	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(resp)
}

// normalizeStatus maps both new (pass/fail/skip) and legacy (ok/error/skipped)
// vocabularies to the canonical pass/fail/skip set. Unknown values are treated
// as skip for safety.
func normalizeStatus(s string) string {
	switch s {
	case "pass", "ok":
		return "pass"
	case "fail", "error":
		return "fail"
	case "skip", "skipped":
		return "skip"
	default:
		return "skip"
	}
}

// parseWindow accepts Go-style durations plus "Nd" for days.
func parseWindow(s string) (time.Duration, error) {
	if strings.HasSuffix(s, "d") {
		// Replace "d" with "h" * 24
		days := strings.TrimSuffix(s, "d")
		d, err := time.ParseDuration(days + "h")
		if err != nil {
			return 0, err
		}
		return d * 24, nil
	}
	return time.ParseDuration(s)
}