package config

import (
	"encoding/json"
	"fmt"
	"io"
	"strconv"
	"strings"
)

// RemoteConfig is the versioned, app-scoped control-plane document offered to TVs. It
// contains behaviour switches and ordering, but never credentials or viewer state. An
// unavailable document is safe because the APK carries equivalent bundled defaults.
type RemoteConfig struct {
	SchemaVersion     int                      `json:"schemaVersion"`
	ConfigVersion     int64                    `json:"configVersion"`
	MinimumAppVersion string                   `json:"minimumAppVersion,omitempty"`
	MaximumAppVersion string                   `json:"maximumAppVersion,omitempty"`
	Copy              RemoteConfigCopy         `json:"copy"`
	Features          RemoteConfigFeatures     `json:"features"`
	Presentation      RemoteConfigPresentation `json:"presentation"`
	Home              RemoteHomeConfig         `json:"home"`
	Movies            RemotePageConfig         `json:"movies"`
	TV                RemotePageConfig         `json:"tv"`
	ContinueWatching  RemoteContinueWatching   `json:"continueWatching"`
	ForYou            RemoteForYouConfig       `json:"forYou"`
	Recommendations   RemoteRecommendations    `json:"recommendations"`
	Search            RemoteSearchConfig       `json:"search"`
	UI                RemoteUIConfig           `json:"ui"`
	Experimental      map[string]bool          `json:"experimental,omitempty"`
	Integrations      RemoteIntegrations       `json:"integrations"`
	Branding          RemoteBranding           `json:"branding"`
}

type RemoteConfigCopy struct {
	Navigation RemoteConfigNavigationCopy `json:"navigation"`
	Tagline    string                     `json:"tagline"`
}

type RemoteConfigNavigationCopy struct {
	Home       string `json:"home"`
	ForYou     string `json:"forYou"`
	Search     string `json:"search"`
	Movies     string `json:"movies"`
	TVShows    string `json:"tvShows"`
	Genres     string `json:"genres"`
	TVCalendar string `json:"tvCalendar"`
	Favourites string `json:"favourites"`
	User       string `json:"user"`
	Settings   string `json:"settings"`
}

type RemoteConfigFeatures struct {
	ShowNavigationVersion bool            `json:"showNavigationVersion"`
	Flags                 map[string]bool `json:"flags,omitempty"`
}

type RemoteConfigPresentation struct {
	NavigationRailExpandedWidthDp int    `json:"navigationRailExpandedWidthDp"`
	NavigationContentShiftDp      int    `json:"navigationContentShiftDp"`
	FontFamily                    string `json:"fontFamily"`
}

// The remainder of the document is deliberately declarative. A new server-side row or
// option can be added to these lists without making the client understand it: older clients
// filter unknown ids and retain their bundled ordering for anything they do not know.
type RemoteHomeConfig struct {
	Sections           []string                  `json:"sections"`
	SectionDefinitions []RemoteSectionDefinition `json:"sectionDefinitions,omitempty"`
	ShowForYou         bool                      `json:"showForYou"`
	ShowSeasonal       bool                      `json:"showSeasonal"`
	HeroRefreshSeconds int                       `json:"heroRefreshSeconds"`
	MaxItemsPerRow     int                       `json:"maxItemsPerRow"`
}

type RemotePageConfig struct {
	Sections           []string                  `json:"sections"`
	SectionDefinitions []RemoteSectionDefinition `json:"sectionDefinitions,omitempty"`
	ShowGenres         bool                      `json:"showGenres"`
}

// RemoteSectionDefinition is the stable composition contract. Clients render only
// known component types and ignore definitions introduced by newer gateways.
type RemoteSectionDefinition struct {
	ID          string `json:"id"`
	Type        string `json:"type"`
	Title       string `json:"title"`
	Enabled     bool   `json:"enabled"`
	Position    int    `json:"position"`
	DataSource  string `json:"dataSource"`
	Component   string `json:"component"`
	MaxItems    int    `json:"maxItems,omitempty"`
	Destination string `json:"destination,omitempty"`
	// Layout overrides the card shape a mediaRow draws: "poster" forces upright poster
	// cards, "thumb" forces the wide landscape cards Continue Watching uses. Empty leaves
	// the client's automatic choice (episodes landscape, everything else poster) alone.
	Layout   string         `json:"layout,omitempty"`
	Settings map[string]any `json:"settings,omitempty"`
}

// SectionLayoutPoster and SectionLayoutThumb are the two explicit card shapes an operator
// can pin a row to; anything else means "let the client decide".
const (
	SectionLayoutPoster = "poster"
	SectionLayoutThumb  = "thumb"
)

type RemoteContinueWatching struct {
	Enabled        bool   `json:"enabled"`
	IncludeNextUp  bool   `json:"includeNextUp"`
	MaxItems       int    `json:"maxItems"`
	ProgressColour string `json:"progressColour"`
}

type RemoteForYouConfig struct {
	Enabled      bool `json:"enabled"`
	MaxRows      int  `json:"maxRows"`
	RefreshHours int  `json:"refreshHours"`
}

type RemoteRecommendations struct {
	Enabled  bool     `json:"enabled"`
	Sections []string `json:"sections"`
}

type RemoteSearchConfig struct {
	Enabled       bool `json:"enabled"`
	GenresEnabled bool `json:"genresEnabled"`
	MaxResults    int  `json:"maxResults"`
}

type RemoteUIConfig struct {
	ArtworkStyle       string `json:"artworkStyle"`
	CardDensity        string `json:"cardDensity"`
	ShowWatchedBadges  bool   `json:"showWatchedBadges"`
	ShowMediaTypeIcons bool   `json:"showMediaTypeIcons"`
}

type RemoteIntegrations struct {
	Tracearr bool `json:"tracearr"`
	Sonarr   bool `json:"sonarr"`
	Radarr   bool `json:"radarr"`
}

type RemoteBranding struct {
	MarkURL     string `json:"markUrl,omitempty"`
	MarkVersion string `json:"markVersion,omitempty"`
}

// DefaultRemoteConfig mirrors the APK's bundled values. Serving it is still useful: it
// establishes the schema and ETag contract before an operator chooses an override.
func DefaultRemoteConfig() RemoteConfig {
	return RemoteConfig{
		SchemaVersion: 1,
		ConfigVersion: 1,
		Copy: RemoteConfigCopy{
			Tagline: "Matt’s Android TV client",
			Navigation: RemoteConfigNavigationCopy{
				Home: "Home", ForYou: "For You", Search: "Search", Movies: "Movies",
				TVShows: "TV Shows", Genres: "Genres", TVCalendar: "TV Calendar", Favourites: "Favourites",
				User: "User", Settings: "Settings",
			},
		},
		Features: RemoteConfigFeatures{
			ShowNavigationVersion: true,
			Flags: map[string]bool{
				"continue_watching": true, "for_you": true, "recommendations": true,
				"genre_browser": false, "tv_calendar": true, "tracearr": false,
				"sonarr": false, "radarr": false,
			},
		},
		Presentation: RemoteConfigPresentation{
			NavigationRailExpandedWidthDp: 184,
			NavigationContentShiftDp:      112,
			FontFamily:                    "system",
		},
		Home: RemoteHomeConfig{
			Sections:           []string{"continue", "for-you", "favorites", "latest-movies"},
			SectionDefinitions: defaultHomeSections(),
			ShowForYou:         true, ShowSeasonal: true, HeroRefreshSeconds: 60, MaxItemsPerRow: 20,
		},
		Movies:           RemotePageConfig{Sections: []string{"genres", "library"}, SectionDefinitions: defaultPageSections("movies"), ShowGenres: false},
		TV:               RemotePageConfig{Sections: []string{"genres", "library"}, SectionDefinitions: defaultPageSections("tv"), ShowGenres: false},
		ContinueWatching: RemoteContinueWatching{Enabled: true, IncludeNextUp: true, MaxItems: 20, ProgressColour: "emby"},
		ForYou:           RemoteForYouConfig{Enabled: true, MaxRows: 3, RefreshHours: 24},
		Recommendations:  RemoteRecommendations{Enabled: true, Sections: []string{"for-you", "because-you-watched"}},
		Search:           RemoteSearchConfig{Enabled: true, GenresEnabled: false, MaxResults: 50},
		UI:               RemoteUIConfig{ArtworkStyle: "automatic", CardDensity: "standard", ShowWatchedBadges: true, ShowMediaTypeIcons: false},
		Experimental:     map[string]bool{},
		Integrations:     RemoteIntegrations{},
		Branding:         RemoteBranding{},
	}
}

func defaultHomeSections() []RemoteSectionDefinition {
	return []RemoteSectionDefinition{
		{ID: "continue", Type: "continueWatching", Title: "Continue Watching", Enabled: true, Position: 10, DataSource: "emby.resume", Component: "mediaRow", MaxItems: 20, Destination: "home"},
		{ID: "for-you", Type: "forYou", Title: "For You", Enabled: true, Position: 20, DataSource: "gateway.recommendations", Component: "mediaRow", MaxItems: 20, Destination: "for-you"},
		{ID: "favorites", Type: "favorites", Title: "Favourites", Enabled: true, Position: 30, DataSource: "emby.favourites", Component: "mediaRow", MaxItems: 20, Destination: "home"},
		{ID: "latest-movies", Type: "latest", Title: "Recently Added", Enabled: true, Position: 40, DataSource: "emby.latest", Component: "mediaRow", MaxItems: 20, Destination: "movies"},
	}
}

func defaultPageSections(destination string) []RemoteSectionDefinition {
	return []RemoteSectionDefinition{
		{ID: "genres", Type: "genres", Title: "Genres", Enabled: true, Position: 10, DataSource: "emby.genres", Component: "genreBrowser", MaxItems: 20, Destination: destination},
		{ID: "library", Type: "library", Title: "Library", Enabled: true, Position: 20, DataSource: "emby.library", Component: "mediaGrid", MaxItems: 20, Destination: destination},
	}
}

func loadRemoteConfig(raw string) (RemoteConfig, error) {
	if strings.TrimSpace(raw) == "" {
		return DefaultRemoteConfig(), nil
	}
	// Start from defaults so a document published before a newly added section remains
	// valid and receives the same safe behaviour as a bundled client.
	document := DefaultRemoteConfig()
	decoder := json.NewDecoder(strings.NewReader(raw))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&document); err != nil {
		return RemoteConfig{}, fmt.Errorf("MEMBY_REMOTE_CONFIG_JSON: %w", err)
	}
	var trailing any
	if err := decoder.Decode(&trailing); err != io.EOF {
		return RemoteConfig{}, fmt.Errorf("MEMBY_REMOTE_CONFIG_JSON must contain exactly one document")
	}
	if err := validateRemoteConfig(document); err != nil {
		return RemoteConfig{}, fmt.Errorf("MEMBY_REMOTE_CONFIG_JSON: %w", err)
	}
	return document, nil
}

func validateRemoteConfig(document RemoteConfig) error {
	if document.SchemaVersion != 1 {
		return fmt.Errorf("schemaVersion must be 1")
	}
	if document.ConfigVersion < 1 {
		return fmt.Errorf("configVersion must be positive")
	}
	minimum, minimumSet, err := parseRemoteConfigVersion(document.MinimumAppVersion)
	if err != nil {
		return fmt.Errorf("minimumAppVersion must be a three-part version")
	}
	maximum, maximumSet, err := parseRemoteConfigVersion(document.MaximumAppVersion)
	if err != nil {
		return fmt.Errorf("maximumAppVersion must be a three-part version")
	}
	if minimumSet && maximumSet && compareRemoteConfigVersions(minimum, maximum) > 0 {
		return fmt.Errorf("minimumAppVersion must not be newer than maximumAppVersion")
	}
	labels := []string{
		document.Copy.Tagline,
		document.Copy.Navigation.Home,
		document.Copy.Navigation.ForYou,
		document.Copy.Navigation.Search,
		document.Copy.Navigation.Movies,
		document.Copy.Navigation.TVShows,
		document.Copy.Navigation.Genres,
		document.Copy.Navigation.TVCalendar,
		document.Copy.Navigation.Favourites,
		document.Copy.Navigation.User,
		document.Copy.Navigation.Settings,
	}
	for _, label := range labels {
		trimmed := strings.TrimSpace(label)
		if trimmed == "" || len([]rune(trimmed)) > 64 || strings.ContainsAny(trimmed, "\r\n\t") {
			return fmt.Errorf("copy must be between 1 and 64 characters and contain no control whitespace")
		}
	}
	width := document.Presentation.NavigationRailExpandedWidthDp
	shift := document.Presentation.NavigationContentShiftDp
	if width < 160 || width > 240 {
		return fmt.Errorf("navigationRailExpandedWidthDp must be between 160 and 240")
	}
	if shift < 80 || shift > 160 || shift >= width {
		return fmt.Errorf("navigationContentShiftDp must be between 80 and 160 and less than the rail width")
	}
	if document.Presentation.FontFamily != "system" && document.Presentation.FontFamily != "inter" {
		return fmt.Errorf("fontFamily must be system or inter")
	}
	if err := validateRemoteConfigSections(document); err != nil {
		return err
	}
	return nil
}

func validateRemoteConfigSections(document RemoteConfig) error {
	if len(document.Home.Sections) > 32 || len(document.Movies.Sections) > 32 || len(document.TV.Sections) > 32 || len(document.Recommendations.Sections) > 32 {
		return fmt.Errorf("section ordering contains too many entries")
	}
	for _, sections := range [][]string{document.Home.Sections, document.Movies.Sections, document.TV.Sections, document.Recommendations.Sections} {
		for _, section := range sections {
			section = strings.TrimSpace(section)
			if section == "" || len(section) > 64 || strings.ContainsAny(section, "\r\n\t") {
				return fmt.Errorf("section ids must be between 1 and 64 characters")
			}
		}
	}
	for key := range document.Features.Flags {
		if strings.TrimSpace(key) == "" || len(key) > 64 {
			return fmt.Errorf("feature flag ids must be between 1 and 64 characters")
		}
	}
	for key := range document.Experimental {
		if strings.TrimSpace(key) == "" || len(key) > 64 {
			return fmt.Errorf("experimental flag ids must be between 1 and 64 characters")
		}
	}
	if document.ContinueWatching.MaxItems < 1 || document.ContinueWatching.MaxItems > 100 {
		return fmt.Errorf("continueWatching.maxItems must be between 1 and 100")
	}
	if document.ForYou.MaxRows < 0 || document.ForYou.MaxRows > 20 || document.ForYou.RefreshHours < 1 || document.ForYou.RefreshHours > 168 {
		return fmt.Errorf("forYou limits are unsafe")
	}
	if document.Search.MaxResults < 1 || document.Search.MaxResults > 200 {
		return fmt.Errorf("search.maxResults must be between 1 and 200")
	}
	if document.UI.ArtworkStyle != "automatic" && document.UI.ArtworkStyle != "poster" && document.UI.ArtworkStyle != "backdrop" {
		return fmt.Errorf("ui.artworkStyle is invalid")
	}
	if document.UI.CardDensity != "standard" && document.UI.CardDensity != "compact" && document.UI.CardDensity != "large" {
		return fmt.Errorf("ui.cardDensity is invalid")
	}
	for _, definitions := range [][]RemoteSectionDefinition{document.Home.SectionDefinitions, document.Movies.SectionDefinitions, document.TV.SectionDefinitions} {
		if len(definitions) > 64 {
			return fmt.Errorf("remote configuration has too many section definitions")
		}
		for _, section := range definitions {
			if strings.TrimSpace(section.ID) == "" || strings.TrimSpace(section.Type) == "" || strings.TrimSpace(section.Component) == "" {
				return fmt.Errorf("remote configuration section definitions require id, type and component")
			}
			if section.Position < 0 || section.MaxItems < 0 || section.MaxItems > 500 {
				return fmt.Errorf("remote configuration section has an invalid position or item limit")
			}
			if section.Layout != "" && section.Layout != SectionLayoutPoster && section.Layout != SectionLayoutThumb {
				return fmt.Errorf("remote configuration section %q has an invalid layout", section.ID)
			}
		}
	}
	return nil
}

func parseRemoteConfigVersion(raw string) ([3]int, bool, error) {
	var version [3]int
	if strings.TrimSpace(raw) == "" {
		return version, false, nil
	}
	parts := strings.Split(raw, ".")
	if len(parts) != len(version) {
		return version, false, fmt.Errorf("invalid version")
	}
	for index, part := range parts {
		value, err := strconv.Atoi(part)
		if err != nil || value < 0 {
			return version, false, fmt.Errorf("invalid version")
		}
		version[index] = value
	}
	return version, true, nil
}

func compareRemoteConfigVersions(left, right [3]int) int {
	for index := range left {
		if left[index] < right[index] {
			return -1
		}
		if left[index] > right[index] {
			return 1
		}
	}
	return 0
}