// Package emby is a small client for the Emby REST API.
//
// Item payloads are deliberately carried as json.RawMessage and forwarded to the TV
// untouched: the Android client already models Emby's item shape, so passing it through
// verbatim means there is no second schema to keep in sync. Only the handful of fields
// the gateway itself reasons about (id, type, resume position) are ever unmarshalled.
package emby

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

type Client struct {
	baseURL    string
	publicURL  string
	clientName string
	http       *http.Client
}

// Credentials identify one signed-in Emby user.
type Credentials struct {
	UserID     string
	Token      string
	DeviceID   string
	DeviceName string
}

type ItemsResult struct {
	Items            []json.RawMessage `json:"Items"`
	TotalRecordCount int               `json:"TotalRecordCount"`
}

type AuthResult struct {
	User struct {
		ID   string `json:"Id"`
		Name string `json:"Name"`
	} `json:"User"`
	AccessToken string `json:"AccessToken"`
	ServerID    string `json:"ServerId"`
}

// Summary is the minimal view of an item the gateway needs for its own logic.
type Summary struct {
	ID       string `json:"Id"`
	Name     string `json:"Name"`
	Type     string `json:"Type"`
	UserData struct {
		PlaybackPositionTicks int64 `json:"PlaybackPositionTicks"`
	} `json:"UserData"`
}

// APIError carries an upstream Emby status code so handlers can mirror it.
type APIError struct {
	StatusCode int
	Body       string
}

func (e *APIError) Error() string {
	return fmt.Sprintf("emby: status %d: %s", e.StatusCode, e.Body)
}

func New(baseURL, publicURL, clientName string, timeout time.Duration) *Client {
	return &Client{
		baseURL:    strings.TrimRight(baseURL, "/"),
		publicURL:  strings.TrimRight(publicURL, "/"),
		clientName: clientName,
		http: &http.Client{
			Timeout: timeout,
			Transport: &http.Transport{
				MaxIdleConns:        100,
				MaxIdleConnsPerHost: 20,
				IdleConnTimeout:     90 * time.Second,
			},
		},
	}
}

func (c *Client) Authenticate(ctx context.Context, username, password, deviceID, deviceName string) (*AuthResult, error) {
	body, err := json.Marshal(map[string]string{"Username": username, "Pw": password})
	if err != nil {
		return nil, err
	}
	req, err := c.newRequest(ctx, http.MethodPost, "/Users/AuthenticateByName", nil,
		Credentials{DeviceID: deviceID, DeviceName: deviceName}, bytes.NewReader(body))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")

	var out AuthResult
	if err := c.do(req, &out); err != nil {
		return nil, err
	}
	if out.AccessToken == "" || out.User.ID == "" {
		return nil, fmt.Errorf("emby: authentication returned no access token")
	}
	return &out, nil
}

// Logout retires a token created during authentication. The gateway uses this when a
// device is refused by policy so Emby is not left holding an orphaned session.
func (c *Client) Logout(ctx context.Context, cred Credentials) error {
	req, err := c.newRequest(ctx, http.MethodPost, "/Sessions/Logout", nil, cred, nil)
	if err != nil {
		return err
	}
	return c.do(req, nil)
}

func (c *Client) Items(ctx context.Context, cred Credentials, params url.Values) (*ItemsResult, error) {
	return c.items(ctx, cred, "/Users/"+url.PathEscape(cred.UserID)+"/Items", params)
}

func (c *Client) NextUp(ctx context.Context, cred Credentials, params url.Values) (*ItemsResult, error) {
	params.Set("UserId", cred.UserID)
	return c.items(ctx, cred, "/Shows/NextUp", params)
}

// Similar asks Emby which items resemble one the user already watched.
func (c *Client) Similar(ctx context.Context, cred Credentials, itemID string, params url.Values) (*ItemsResult, error) {
	params.Set("UserId", cred.UserID)
	return c.items(ctx, cred, "/Items/"+url.PathEscape(itemID)+"/Similar", params)
}

func (c *Client) Episodes(ctx context.Context, cred Credentials, seriesID string, params url.Values) (*ItemsResult, error) {
	params.Set("UserId", cred.UserID)
	return c.items(ctx, cred, "/Shows/"+url.PathEscape(seriesID)+"/Episodes", params)
}

// LocalTrailers returns the trailers Emby holds locally for an item.
func (c *Client) LocalTrailers(ctx context.Context, cred Credentials, itemID string) (*ItemsResult, error) {
	path := "/Users/" + url.PathEscape(cred.UserID) + "/Items/" + url.PathEscape(itemID) + "/LocalTrailers"
	req, err := c.newRequest(ctx, http.MethodGet, path, nil, cred, nil)
	if err != nil {
		return nil, err
	}
	// This endpoint answers with a bare array rather than an Items envelope.
	var items []json.RawMessage
	if err := c.do(req, &items); err != nil {
		return nil, err
	}
	return &ItemsResult{Items: items, TotalRecordCount: len(items)}, nil
}

func (c *Client) Item(ctx context.Context, cred Credentials, itemID, fields string) (json.RawMessage, error) {
	params := url.Values{}
	if fields != "" {
		params.Set("Fields", fields)
	}
	path := "/Users/" + url.PathEscape(cred.UserID) + "/Items/" + url.PathEscape(itemID)
	req, err := c.newRequest(ctx, http.MethodGet, path, params, cred, nil)
	if err != nil {
		return nil, err
	}
	var raw json.RawMessage
	if err := c.do(req, &raw); err != nil {
		return nil, err
	}
	return raw, nil
}

// SetFavorite/SetPlayed return Emby's resulting UserData verbatim.
func (c *Client) SetFavorite(ctx context.Context, cred Credentials, itemID string, favorite bool) (json.RawMessage, error) {
	method := http.MethodDelete
	if favorite {
		method = http.MethodPost
	}
	path := "/Users/" + url.PathEscape(cred.UserID) + "/FavoriteItems/" + url.PathEscape(itemID)
	return c.userDataCall(ctx, method, path, cred)
}

func (c *Client) SetPlayed(ctx context.Context, cred Credentials, itemID string, played bool) (json.RawMessage, error) {
	method := http.MethodDelete
	if played {
		method = http.MethodPost
	}
	path := "/Users/" + url.PathEscape(cred.UserID) + "/PlayedItems/" + url.PathEscape(itemID)
	return c.userDataCall(ctx, method, path, cred)
}

// ReportPlayback forwards a progress report. phase is "started", "progress" or "stopped".
func (c *Client) ReportPlayback(ctx context.Context, cred Credentials, phase string, itemID string, positionTicks int64, isPaused bool) error {
	var path string
	switch phase {
	case "started":
		path = "/Sessions/Playing"
	case "progress":
		path = "/Sessions/Playing/Progress"
	case "stopped":
		path = "/Sessions/Playing/Stopped"
	default:
		return fmt.Errorf("emby: unknown playback phase %q", phase)
	}

	body, err := json.Marshal(map[string]any{
		"ItemId":        itemID,
		"PositionTicks": positionTicks,
		"IsPaused":      isPaused,
		"IsMuted":       false,
		"CanSeek":       true,
		"PlayMethod":    "DirectPlay",
	})
	if err != nil {
		return err
	}
	req, err := c.newRequest(ctx, http.MethodPost, path, nil, cred, bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")
	return c.do(req, nil)
}

// ImageResponse streams an image straight from Emby so the caller can copy it to the TV.
// The caller owns closing the body.
func (c *Client) ImageResponse(ctx context.Context, cred Credentials, itemID, imageType string, params url.Values) (*http.Response, error) {
	path := "/Items/" + url.PathEscape(itemID) + "/Images/" + url.PathEscape(imageType)
	req, err := c.newRequest(ctx, http.MethodGet, path, params, cred, nil)
	if err != nil {
		return nil, err
	}
	resp, err := c.http.Do(req)
	if err != nil {
		return nil, err
	}
	if resp.StatusCode >= 400 {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
		resp.Body.Close()
		return nil, &APIError{StatusCode: resp.StatusCode, Body: string(body)}
	}
	return resp, nil
}

// StreamURL is the direct-play URL handed to the TV. It points at the *public* Emby
// address: video never flows through the gateway, only metadata does.
func (c *Client) StreamURL(cred Credentials, itemID string) string {
	params := url.Values{}
	params.Set("static", "true")
	params.Set("api_key", cred.Token)
	params.Set("DeviceId", cred.DeviceID)
	return fmt.Sprintf("%s/Videos/%s/stream?%s", c.publicURL, url.PathEscape(itemID), params.Encode())
}

// Ping checks that Emby is reachable, for readiness probes.
func (c *Client) Ping(ctx context.Context) error {
	req, err := c.newRequest(ctx, http.MethodGet, "/System/Info/Public", nil, Credentials{}, nil)
	if err != nil {
		return err
	}
	return c.do(req, nil)
}

func (c *Client) items(ctx context.Context, cred Credentials, path string, params url.Values) (*ItemsResult, error) {
	req, err := c.newRequest(ctx, http.MethodGet, path, params, cred, nil)
	if err != nil {
		return nil, err
	}
	var out ItemsResult
	if err := c.do(req, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

func (c *Client) userDataCall(ctx context.Context, method, path string, cred Credentials) (json.RawMessage, error) {
	req, err := c.newRequest(ctx, method, path, nil, cred, nil)
	if err != nil {
		return nil, err
	}
	var raw json.RawMessage
	if err := c.do(req, &raw); err != nil {
		return nil, err
	}
	return raw, nil
}

func (c *Client) newRequest(ctx context.Context, method, path string, params url.Values, cred Credentials, body io.Reader) (*http.Request, error) {
	full := c.baseURL + path
	if len(params) > 0 {
		full += "?" + params.Encode()
	}
	req, err := http.NewRequestWithContext(ctx, method, full, body)
	if err != nil {
		return nil, err
	}

	deviceID := cred.DeviceID
	if deviceID == "" {
		deviceID = "memby-gateway"
	}
	deviceName := strings.TrimSpace(cred.DeviceName)
	if deviceName == "" {
		deviceName = "Memby TV"
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("X-Emby-Authorization", fmt.Sprintf(
		`MediaBrowser Client="%s", Device="%s", DeviceId="%s", Version="1.0"`,
		c.clientName, strings.ReplaceAll(deviceName, `"`, ""), deviceID,
	))
	if cred.Token != "" {
		req.Header.Set("X-Emby-Token", cred.Token)
	}
	return req, nil
}

// do executes a request and decodes into out (which may be nil to discard the body).
func (c *Client) do(req *http.Request, out any) error {
	resp, err := c.http.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 400 {
		// Emby error bodies can echo request details; cap what we keep and never log it
		// alongside a token.
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 2048))
		return &APIError{StatusCode: resp.StatusCode, Body: string(body)}
	}
	if out == nil {
		_, _ = io.Copy(io.Discard, resp.Body)
		return nil
	}
	return json.NewDecoder(resp.Body).Decode(out)
}

// Summarise unmarshals the fields the gateway reasons about from a raw item.
func Summarise(raw json.RawMessage) (Summary, error) {
	var s Summary
	err := json.Unmarshal(raw, &s)
	return s, err
}