package mediaserver

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

// ServerConfig describes a media server that should be refreshed after a
// download (or .strm write) finishes. Stored in unarr's config.toml under
// [[mediaserver]].
type ServerConfig struct {
	Kind     string `toml:"kind"`     // "plex" | "jellyfin" | "emby"
	URL      string `toml:"url"`      // e.g. http://localhost:32400
	Token    string `toml:"token"`    // Plex token / Jellyfin or Emby API key
	Sections []int  `toml:"sections"` // optional: Plex section IDs to refresh (else auto)
}

// Section describes a Plex library section.
type Section struct {
	ID        int
	Title     string
	Locations []string
}

// httpClient is the shared HTTP client for refresh calls. Short timeouts
// because a refresh trigger is fire-and-forget.
var httpClient = &http.Client{Timeout: 8 * time.Second}

// plexSectionCache caches section lookups per server URL+token, so we don't
// re-fetch sections on every download.
var (
	plexSectionMu    sync.RWMutex
	plexSectionCache = map[string][]Section{}
)

// Refresh fans out a refresh call to every configured media server. Errors
// are logged but never returned — a failed refresh is non-fatal because the
// download itself succeeded and the next periodic scan will pick it up.
//
// `filePath` is the path of the file that was just placed (or the .strm
// pointer); it's used to resolve the matching Plex section for partial
// refreshes. Pass "" to fall back to a full refresh.
//
// Each refresh runs in its own goroutine with a 15s timeout — the call
// returns immediately and never blocks the caller.
func Refresh(servers []ServerConfig, filePath string) {
	for _, s := range servers {
		go func() {
			ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
			defer cancel()
			if err := refreshOne(ctx, s, filePath); err != nil {
				log.Printf("mediaserver: %s refresh failed (%s): %v", s.Kind, s.URL, err)
			}
		}()
	}
}

func refreshOne(ctx context.Context, s ServerConfig, filePath string) error {
	switch strings.ToLower(s.Kind) {
	case "plex":
		return refreshPlex(ctx, s, filePath)
	case "jellyfin", "emby":
		return refreshJellyfin(ctx, s)
	default:
		return fmt.Errorf("unknown kind %q", s.Kind)
	}
}

// ── Plex ────────────────────────────────────────────────────────────

func refreshPlex(ctx context.Context, s ServerConfig, filePath string) error {
	if s.URL == "" || s.Token == "" {
		return fmt.Errorf("plex: missing url or token")
	}

	sectionIDs := s.Sections
	if len(sectionIDs) == 0 {
		// Auto-resolve: fetch sections, pick whichever owns the file path.
		sections, err := plexSections(ctx, s.URL, s.Token)
		if err != nil {
			return fmt.Errorf("fetch sections: %w", err)
		}
		if filePath != "" {
			if id, ok := matchSectionByPath(sections, filePath); ok {
				sectionIDs = []int{id}
			}
		}
		if len(sectionIDs) == 0 {
			// Fall back to refreshing every section.
			for _, sec := range sections {
				sectionIDs = append(sectionIDs, sec.ID)
			}
		}
	}

	var firstErr error
	for _, id := range sectionIDs {
		if err := plexRefreshSection(ctx, s.URL, s.Token, id, filePath); err != nil {
			if firstErr == nil {
				firstErr = err
			}
			log.Printf("mediaserver: plex section %d refresh failed: %v", id, err)
		}
	}
	return firstErr
}

func plexRefreshSection(ctx context.Context, baseURL, token string, sectionID int, filePath string) error {
	q := url.Values{}
	if filePath != "" {
		q.Set("path", filePath)
	}
	q.Set("X-Plex-Token", token)

	endpoint := fmt.Sprintf("%s/library/sections/%d/refresh?%s",
		strings.TrimRight(baseURL, "/"), sectionID, q.Encode())

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return err
	}
	req.Header.Set("Accept", "application/json")

	resp, err := httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	_, _ = io.Copy(io.Discard, resp.Body)

	if resp.StatusCode >= 200 && resp.StatusCode < 300 {
		return nil
	}
	return fmt.Errorf("status %d", resp.StatusCode)
}

// plexSections returns the cached or freshly fetched library sections for a
// Plex server. The cache lives for the agent's lifetime — Plex sections
// rarely change, so refetching on every download is wasteful.
func plexSections(ctx context.Context, baseURL, token string) ([]Section, error) {
	key := baseURL + "|" + token
	plexSectionMu.RLock()
	cached, ok := plexSectionCache[key]
	plexSectionMu.RUnlock()
	if ok {
		return cached, nil
	}

	sections, err := fetchPlexSections(ctx, baseURL, token)
	if err != nil {
		return nil, err
	}

	plexSectionMu.Lock()
	plexSectionCache[key] = sections
	plexSectionMu.Unlock()

	return sections, nil
}

func fetchPlexSections(ctx context.Context, baseURL, token string) ([]Section, error) {
	endpoint := strings.TrimRight(baseURL, "/") + "/library/sections"
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("X-Plex-Token", token)
	req.Header.Set("Accept", "application/json")

	resp, err := httpClient.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("status %d", resp.StatusCode)
	}

	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return nil, err
	}

	return parsePlexSectionsFull(body)
}

// parsePlexSectionsFull parses the full sections response with IDs.
func parsePlexSectionsFull(body []byte) ([]Section, error) {
	var container struct {
		MediaContainer struct {
			Directory []struct {
				Key      string `json:"key"`
				Title    string `json:"title"`
				Location []struct {
					Path string `json:"path"`
				} `json:"Location"`
			} `json:"Directory"`
		} `json:"MediaContainer"`
	}
	if err := json.Unmarshal(body, &container); err != nil {
		return nil, err
	}

	var out []Section
	for _, d := range container.MediaContainer.Directory {
		var id int
		_, _ = fmt.Sscanf(d.Key, "%d", &id)
		if id == 0 {
			continue
		}
		sec := Section{ID: id, Title: d.Title}
		for _, loc := range d.Location {
			if loc.Path != "" {
				sec.Locations = append(sec.Locations, loc.Path)
			}
		}
		out = append(out, sec)
	}
	return out, nil
}

// matchSectionByPath returns the ID of the section whose Locations contain
// (as prefix) the given file path. Picks the most specific (longest) match.
func matchSectionByPath(sections []Section, filePath string) (int, bool) {
	bestID := 0
	bestLen := 0
	for _, s := range sections {
		for _, loc := range s.Locations {
			loc = strings.TrimRight(loc, "/")
			if loc == "" {
				continue
			}
			if filePath == loc || strings.HasPrefix(filePath, loc+"/") {
				if len(loc) > bestLen {
					bestLen = len(loc)
					bestID = s.ID
				}
			}
		}
	}
	return bestID, bestID != 0
}

// ── Jellyfin / Emby ─────────────────────────────────────────────────

func refreshJellyfin(ctx context.Context, s ServerConfig) error {
	if s.URL == "" || s.Token == "" {
		return fmt.Errorf("%s: missing url or token", s.Kind)
	}

	endpoint := strings.TrimRight(s.URL, "/") + "/Library/Refresh"
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, nil)
	if err != nil {
		return err
	}
	// Both Jellyfin and Emby accept this header.
	req.Header.Set("X-Emby-Token", s.Token)
	req.Header.Set("Accept", "application/json")

	resp, err := httpClient.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	_, _ = io.Copy(io.Discard, resp.Body)

	if resp.StatusCode >= 200 && resp.StatusCode < 300 {
		return nil
	}
	return fmt.Errorf("status %d", resp.StatusCode)
}