package httpapi

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

type providerStatus struct {
	Name       string `json:"name"`
	Configured bool   `json:"configured"`
	OK         bool   `json:"ok"`
	Stale      bool   `json:"stale,omitempty"`
	URL        string `json:"url,omitempty"`
	Model      string `json:"model,omitempty"`
	LatencyMS  int64  `json:"latency_ms,omitempty"`
	LastOKAt   string `json:"last_ok_at,omitempty"`
	Error      string `json:"error,omitempty"`
}

type providersStatusResponse struct {
	At        time.Time        `json:"at"`
	Providers []providerStatus `json:"providers"`
}

type providerHealthSnapshot struct {
	at        time.Time
	latencyMS int64
}

const providerStaleOKWindow = 2 * time.Minute

func (s *Server) handleProviderStatus(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := contextWithTimeout(r, 8*time.Second)
	defer cancel()

	resp := providersStatusResponse{
		At: time.Now().UTC(),
		Providers: []providerStatus{
			s.checkLLM(ctx),
			s.checkAudioLLM(ctx, "voxtral-small", s.cfg.VoxtralBaseURL, s.cfg.VoxtralAPIKey, s.cfg.VoxtralModel, s.cfg.VoxtralTimeout),
		},
	}
	writeJSON(w, http.StatusOK, resp)
}

func (s *Server) checkAudioLLM(ctx context.Context, name, baseURL, apiKey, model string, timeout time.Duration) providerStatus {
	baseURL = strings.TrimRight(strings.TrimSpace(baseURL), "/")
	st := providerStatus{
		Name:       name,
		Configured: baseURL != "",
		URL:        baseURL,
		Model:      model,
	}
	if !st.Configured {
		return st
	}
	if timeout <= 0 {
		timeout = 10 * time.Minute
	}
	start := time.Now()
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, st.URL+"/v1/models", nil)
	if err != nil {
		st.Error = err.Error()
		return st
	}
	if apiKey != "" {
		req.Header.Set("Authorization", "Bearer "+apiKey)
	}
	res, err := (&http.Client{Timeout: minDuration(timeout, 3*time.Second)}).Do(req)
	st.LatencyMS = time.Since(start).Milliseconds()
	if err != nil {
		st.Error = err.Error()
		return s.withStaleProviderOK(name, st)
	}
	defer res.Body.Close()
	if res.StatusCode >= 300 {
		st.Error = fmt.Sprintf("http %d: %s", res.StatusCode, readSmallBody(res.Body))
		return s.withStaleProviderOK(name, st)
	}
	st.OK = true
	s.rememberProviderOK(name, st.LatencyMS)
	return st
}

func minDuration(a, b time.Duration) time.Duration {
	if a < b {
		return a
	}
	return b
}

func (s *Server) checkLLM(ctx context.Context) providerStatus {
	st := providerStatus{
		Name:       "llm",
		Configured: strings.TrimSpace(s.cfg.LLMBaseURL) != "",
		URL:        strings.TrimRight(s.cfg.LLMBaseURL, "/"),
		Model:      s.cfg.LLMModel,
	}
	if !st.Configured {
		return st
	}
	start := time.Now()
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, st.URL+"/v1/models", nil)
	if err != nil {
		st.Error = err.Error()
		return st
	}
	if s.cfg.LLMAPIKey != "" {
		req.Header.Set("Authorization", "Bearer "+s.cfg.LLMAPIKey)
	}
	httpClient := &http.Client{Timeout: s.cfg.LLMTimeout}
	res, err := httpClient.Do(req)
	st.LatencyMS = time.Since(start).Milliseconds()
	if err != nil {
		st.Error = err.Error()
		return s.withStaleProviderOK("llm", st)
	}
	defer res.Body.Close()
	if res.StatusCode >= 300 {
		st.Error = fmt.Sprintf("http %d: %s", res.StatusCode, readSmallBody(res.Body))
		return s.withStaleProviderOK("llm", st)
	}
	st.OK = true
	s.rememberProviderOK("llm", st.LatencyMS)
	return st
}

func (s *Server) rememberProviderOK(name string, latencyMS int64) {
	s.providerMu.Lock()
	defer s.providerMu.Unlock()
	s.providerOKs[name] = providerHealthSnapshot{at: time.Now().UTC(), latencyMS: latencyMS}
}

func (s *Server) withStaleProviderOK(name string, st providerStatus) providerStatus {
	s.providerMu.Lock()
	snap, ok := s.providerOKs[name]
	s.providerMu.Unlock()
	if !ok || time.Since(snap.at) > providerStaleOKWindow {
		return st
	}
	st.OK = true
	st.Stale = true
	if st.LatencyMS == 0 {
		st.LatencyMS = snap.latencyMS
	}
	st.LastOKAt = snap.at.Format(time.RFC3339)
	if st.Error != "" {
		st.Error = "последняя проверка не ответила: " + st.Error
	}
	return st
}

func readSmallBody(r io.Reader) string {
	body, err := io.ReadAll(io.LimitReader(r, 512))
	if err != nil {
		return err.Error()
	}
	var parsed map[string]any
	if err := json.Unmarshal(body, &parsed); err == nil {
		if msg, ok := parsed["error"].(string); ok {
			return msg
		}
		if msg, ok := parsed["detail"].(string); ok {
			return msg
		}
	}
	return strings.TrimSpace(string(body))
}