// Package api is a minimal Jellyfin REST client: just enough to authenticate,
// list libraries and their contents, resolve a direct-play stream URL for mpv,
// and report playback progress so "Continue Watching" and resume points work.
//
// All requests carry the Emby-style Authorization header. Before login only the
// client/device fields are set; after login the token is added as Token=.
package api

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

// Version is stamped into the Authorization header and User-Agent.
const Version = "1.0.0"

// Client talks to one Jellyfin server as one user.
type Client struct {
	BaseURL  string // e.g. https://media.example.com (no trailing slash)
	Token    string // access token; empty before login
	UserID   string // logged-in user id; empty before login
	DeviceID string // stable per-install id
	http     *http.Client
}

// New builds a Client. baseURL may have a trailing slash; it is trimmed.
func New(baseURL, token, userID, deviceID string) *Client {
	return &Client{
		BaseURL:  strings.TrimRight(baseURL, "/"),
		Token:    token,
		UserID:   userID,
		DeviceID: deviceID,
		http:     &http.Client{Timeout: 30 * time.Second},
	}
}

// authHeader builds the MediaBrowser authorization header. Token is included
// only once we have one (post-login).
func (c *Client) authHeader() string {
	h := fmt.Sprintf(`MediaBrowser Client="tsplay", Device="tsplay-tui", DeviceId=%q, Version=%q`,
		c.DeviceID, Version)
	if c.Token != "" {
		h += fmt.Sprintf(`, Token=%q`, c.Token)
	}
	return h
}

func (c *Client) do(ctx context.Context, method, path string, body any, out any) error {
	var rdr io.Reader
	if body != nil {
		b, err := json.Marshal(body)
		if err != nil {
			return err
		}
		rdr = bytes.NewReader(b)
	}
	req, err := http.NewRequestWithContext(ctx, method, c.BaseURL+path, rdr)
	if err != nil {
		return err
	}
	req.Header.Set("Authorization", c.authHeader())
	req.Header.Set("User-Agent", "tsplay/"+Version)
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	resp, err := c.http.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		msg, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
		return fmt.Errorf("%s %s: %s: %s", method, path, resp.Status, strings.TrimSpace(string(msg)))
	}
	if out != nil {
		return json.NewDecoder(resp.Body).Decode(out)
	}
	return nil
}

// AuthResult is the subset of AuthenticateByName we care about.
type AuthResult struct {
	AccessToken string `json:"AccessToken"`
	User        struct {
		ID   string `json:"Id"`
		Name string `json:"Name"`
	} `json:"User"`
}

// Login authenticates by username/password and populates Token/UserID on the
// client. Returns the result so the caller can persist it.
func (c *Client) Login(ctx context.Context, username, password string) (*AuthResult, error) {
	var res AuthResult
	body := map[string]string{"Username": username, "Pw": password}
	if err := c.do(ctx, http.MethodPost, "/Users/AuthenticateByName", body, &res); err != nil {
		return nil, err
	}
	if res.AccessToken == "" {
		return nil, fmt.Errorf("login failed: no access token returned")
	}
	c.Token = res.AccessToken
	c.UserID = res.User.ID
	return &res, nil
}

// Item is a generic Jellyfin item (library, folder, movie, episode, audio…).
// Only the fields the TUI needs are mapped.
type Item struct {
	ID                string `json:"Id"`
	Name              string `json:"Name"`
	Type              string `json:"Type"`           // Movie, Series, Season, Episode, Audio, MusicAlbum, CollectionFolder…
	CollectionType    string `json:"CollectionType"` // movies, tvshows, music… (on libraries)
	IsFolder          bool   `json:"IsFolder"`
	ProductionYear    int    `json:"ProductionYear"`
	RunTimeTicks      int64  `json:"RunTimeTicks"` // 1 tick = 100ns
	SeriesName        string `json:"SeriesName"`
	IndexNumber       int    `json:"IndexNumber"`       // episode/track number
	ParentIndexNumber int    `json:"ParentIndexNumber"` // season number
	UserData          struct {
		PlaybackPositionTicks int64   `json:"PlaybackPositionTicks"`
		PlayedPercentage      float64 `json:"PlayedPercentage"`
		Played                bool    `json:"Played"`
	} `json:"UserData"`
}

// Playable reports whether selecting this item should start mpv rather than
// drill into a folder.
func (i Item) Playable() bool {
	switch i.Type {
	case "Movie", "Episode", "Audio", "Video", "MusicVideo":
		return true
	}
	return !i.IsFolder
}

// AudioOnly reports whether this item is music (so mpv should run headless,
// with no video window). MusicVideo is intentionally excluded — it has a
// picture worth showing.
func (i Item) AudioOnly() bool {
	switch i.Type {
	case "Audio", "MusicAlbum", "MusicArtist":
		return true
	}
	return false
}

type itemsResponse struct {
	Items []Item `json:"Items"`
}

// Views returns the user's top-level libraries (Movies, Shows, Music…).
func (c *Client) Views(ctx context.Context) ([]Item, error) {
	var r itemsResponse
	err := c.do(ctx, http.MethodGet, "/Users/"+c.UserID+"/Views", nil, &r)
	return r.Items, err
}

// Children lists the items directly under parentID for this user, sorted
// sensibly for browsing. recursive=false keeps it one level at a time.
func (c *Client) Children(ctx context.Context, parentID string) ([]Item, error) {
	q := url.Values{}
	q.Set("ParentId", parentID)
	q.Set("SortBy", "IsFolder,SortName")
	q.Set("SortOrder", "Ascending")
	q.Set("Fields", "ProductionYear,SeriesName,IndexNumber,ParentIndexNumber")
	var r itemsResponse
	err := c.do(ctx, http.MethodGet, "/Users/"+c.UserID+"/Items?"+q.Encode(), nil, &r)
	return r.Items, err
}

// Resume returns the user's "Continue Watching" list across all libraries.
func (c *Client) Resume(ctx context.Context) ([]Item, error) {
	q := url.Values{}
	q.Set("Limit", "24")
	q.Set("Fields", "ProductionYear,SeriesName,IndexNumber,ParentIndexNumber")
	q.Set("MediaTypes", "Video")
	var r itemsResponse
	err := c.do(ctx, http.MethodGet, "/Users/"+c.UserID+"/Items/Resume?"+q.Encode(), nil, &r)
	return r.Items, err
}

// StreamURL returns a direct-play URL mpv can open. static=true asks the server
// not to transcode; mpv handles nearly every container/codec natively. The
// api_key query param authenticates the bare GET that mpv makes.
func (c *Client) StreamURL(itemID string) string {
	q := url.Values{}
	q.Set("static", "true")
	q.Set("api_key", c.Token)
	return fmt.Sprintf("%s/Videos/%s/stream?%s", c.BaseURL, itemID, q.Encode())
}

// ReportStart tells the server playback began (creates a session row, marks the
// item as being watched). Best-effort: errors are returned but callers may
// ignore them.
func (c *Client) ReportStart(ctx context.Context, itemID string) error {
	body := map[string]any{"ItemId": itemID, "PlayMethod": "DirectStream"}
	return c.do(ctx, http.MethodPost, "/Sessions/Playing", body, nil)
}

// ReportProgress updates the resume point (positionTicks) periodically.
func (c *Client) ReportProgress(ctx context.Context, itemID string, positionTicks int64, paused bool) error {
	body := map[string]any{"ItemId": itemID, "PositionTicks": positionTicks, "IsPaused": paused, "PlayMethod": "DirectStream"}
	return c.do(ctx, http.MethodPost, "/Sessions/Playing/Progress", body, nil)
}

// ReportStop finalises the resume point when playback ends.
func (c *Client) ReportStop(ctx context.Context, itemID string, positionTicks int64) error {
	body := map[string]any{"ItemId": itemID, "PositionTicks": positionTicks}
	return c.do(ctx, http.MethodPost, "/Sessions/Playing/Stopped", body, nil)
}

// SecondsToTicks converts a position in seconds to Jellyfin's 100ns ticks.
func SecondsToTicks(s float64) int64 { return int64(s * 1e7) }