package handler

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

	"github.com/jackc/pgx/v5/pgxpool"

	"learning-service/internal/storage"
)

type HealthHandler struct {
	pool  *pgxpool.Pool
	store *storage.Storage
}

func NewHealthHandler(pool *pgxpool.Pool, store *storage.Storage) *HealthHandler {
	return &HealthHandler{pool: pool, store: store}
}

// Healthz — liveness. Не дёргает БД; жив если процесс отвечает.
func (h *HealthHandler) Healthz(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

// Readyz — readiness. Один Ping к БД с таймаутом — если не отвечает,
// k8s выкидывает pod из service-балансира.
func (h *HealthHandler) Readyz(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
	defer cancel()
	if err := h.pool.Ping(ctx); err != nil {
		writeError(w, http.StatusServiceUnavailable, "db not ready")
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "ready"})
}

func (h *HealthHandler) Detail(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 3*time.Second)
	defer cancel()

	components := []componentProbe{
		h.probePostgres(ctx),
		h.probeVideoStorage(ctx),
		h.probeVideoMetadata(ctx),
	}
	writeJSON(w, http.StatusOK, map[string]any{"components": components})
}

type componentProbe struct {
	Name      string `json:"name"`
	Status    string `json:"status"`
	LatencyMs int64  `json:"latency_ms"`
	Error     string `json:"error,omitempty"`
}

func (h *HealthHandler) probePostgres(ctx context.Context) componentProbe {
	start := time.Now()
	if err := h.pool.Ping(ctx); err != nil {
		return componentProbe{Name: "postgres", Status: "down", LatencyMs: time.Since(start).Milliseconds(), Error: err.Error()}
	}
	return componentProbe{Name: "postgres", Status: "ok", LatencyMs: time.Since(start).Milliseconds()}
}

func (h *HealthHandler) probeVideoStorage(ctx context.Context) componentProbe {
	start := time.Now()
	if err := h.store.Check(ctx); err != nil {
		return componentProbe{Name: "video_storage", Status: "down", LatencyMs: time.Since(start).Milliseconds(), Error: err.Error()}
	}
	return componentProbe{Name: "video_storage", Status: "ok", LatencyMs: time.Since(start).Milliseconds()}
}

func (h *HealthHandler) probeVideoMetadata(ctx context.Context) componentProbe {
	start := time.Now()
	var videos, broken int
	err := h.pool.QueryRow(ctx, `
		SELECT
			COUNT(*) FILTER (WHERE video_key <> '')::int,
			COUNT(*) FILTER (WHERE video_key <> '' AND btrim(video_key) = '')::int
		FROM lessons`,
	).Scan(&videos, &broken)
	if err != nil {
		return componentProbe{Name: "video_metadata", Status: "down", LatencyMs: time.Since(start).Milliseconds(), Error: err.Error()}
	}
	if broken > 0 {
		return componentProbe{
			Name:      "video_metadata",
			Status:    "down",
			LatencyMs: time.Since(start).Milliseconds(),
			Error:     "videos=" + intString(videos) + " broken_video_keys=" + intString(broken),
		}
	}
	return componentProbe{Name: "video_metadata", Status: "ok", LatencyMs: time.Since(start).Milliseconds()}
}

func intString(v int) string {
	return strconv.Itoa(v)
}