package api

import (
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"net/http"
	"strconv"
	"strings"

	"github.com/ponzischeme89/memby/server/internal/config"
	"github.com/ponzischeme89/memby/server/internal/store"
)

// handleRemoteConfig serves one app-scoped, versioned document. It is public
// for the same reason the update verdict is public: a fresh install and a signed-out TV
// must be able to warm the next launch. No viewer or session data belongs in this answer.
func (s *Server) handleRemoteConfig(w http.ResponseWriter, r *http.Request) {
	document := s.cfg.RemoteConfig
	clientSchema := parseClientSchema(r)
	components := parseCapabilities(r.Header.Get("X-Memby-Components"))
	if clientSchema > 0 && clientSchema < document.SchemaVersion {
		document.SchemaVersion = clientSchema
	}
	policy := s.currentFeaturePolicy(r.Context())
	applyGlobalConfiguration(&document, policy)
	negotiateRemoteSections(&document, components)
	if s.log != nil {
		s.loggerFor(r.Context()).Info("remote configuration delivered", "client_version", r.Header.Get("X-Memby-Version"), "schema", clientSchema, "delivered_schema", document.SchemaVersion, "components", components, "config_version", document.ConfigVersion)
	}
	body, err := json.Marshal(document)
	if err != nil {
		// Config is validated during start-up, so this is defensive rather than an expected
		// operational failure.
		writeError(w, http.StatusInternalServerError, "remote configuration unavailable")
		return
	}
	digest := sha256.Sum256(body)
	etag := `"rc-` + hex.EncodeToString(digest[:12]) + `"`
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("ETag", etag)
	w.Header().Set("X-Memby-Config-Version", configVersionHeader(document.ConfigVersion))
	w.Header().Set("X-Memby-Delivered-Schema", strconv.Itoa(document.SchemaVersion))
	w.Header().Set("X-Memby-Delivered-Components", strings.Join(components, ","))
	if r.Header.Get("If-None-Match") == etag {
		w.WriteHeader(http.StatusNotModified)
		return
	}
	writeRaw(w, http.StatusOK, body)
}

func parseClientSchema(r *http.Request) int {
	value, _ := strconv.Atoi(strings.TrimSpace(r.Header.Get("X-Memby-Config-Schema")))
	return value
}

func negotiateRemoteSections(document *config.RemoteConfig, components []string) {
	if len(components) == 0 {
		return
	}
	supported := make(map[string]bool, len(components))
	for _, component := range components {
		supported[component] = true
	}
	for _, sections := range []*[]config.RemoteSectionDefinition{&document.Home.SectionDefinitions, &document.Movies.SectionDefinitions, &document.TV.SectionDefinitions} {
		for index := range *sections {
			section := &(*sections)[index]
			if supported[section.Component] {
				continue
			}
			if section.Component == "landscapeMediaCardV2" && supported["mediaRow"] {
				section.Component = "mediaRow"
				continue
			}
			section.Enabled = false
		}
	}
}

// applyGlobalConfiguration is intentionally small and typed. The public startup
// document has no viewer identity, so user/device assignments are resolved by the
// authenticated feature endpoint rather than leaking into this cacheable response.
func applyGlobalConfiguration(document *config.RemoteConfig, policy store.FeaturePolicy) {
	for key, raw := range policy.Values {
		var value any
		if json.Unmarshal(raw, &value) != nil {
			continue
		}
		switch key {
		case "forYou.enabled":
			if v, ok := value.(bool); ok {
				document.ForYou.Enabled = v
				document.Features.Flags["forYou.enabled"] = v
				document.Features.Flags["for_you"] = v
			}
		case "continueWatching.enabled":
			if v, ok := value.(bool); ok {
				document.ContinueWatching.Enabled = v
				document.Features.Flags["continueWatching.enabled"] = v
				document.Features.Flags["continue_watching"] = v
			}
		case "continueWatching.showNextUp":
			if v, ok := value.(bool); ok {
				document.ContinueWatching.IncludeNextUp = v
			}
		case "continueWatching.progressColour":
			if v, ok := value.(string); ok {
				document.ContinueWatching.ProgressColour = v
			}
		case "presentation.fontFamily":
			if v, ok := value.(string); ok && (v == "system" || v == "inter") {
				document.Presentation.FontFamily = v
			}
		case "home.heroRefreshSeconds":
			if v, ok := value.(float64); ok {
				document.Home.HeroRefreshSeconds = int(v)
			}
		case "home.maxItemsPerRow":
			if v, ok := value.(float64); ok {
				document.Home.MaxItemsPerRow = int(v)
			}
		case "home.sectionDefinitions":
			if err := json.Unmarshal(raw, &document.Home.SectionDefinitions); err == nil {
				document.Home.Sections = sectionIDs(document.Home.SectionDefinitions)
			}
		case "movies.sectionDefinitions":
			if err := json.Unmarshal(raw, &document.Movies.SectionDefinitions); err == nil {
				document.Movies.Sections = sectionIDs(document.Movies.SectionDefinitions)
			}
		case "tv.sectionDefinitions":
			if err := json.Unmarshal(raw, &document.TV.SectionDefinitions); err == nil {
				document.TV.Sections = sectionIDs(document.TV.SectionDefinitions)
			}
		case "hero.enabled":
			if v, ok := value.(bool); ok {
				document.Features.Flags["hero.enabled"] = v
			}
		case "branding.markUrl":
			if v, ok := value.(string); ok {
				document.Branding.MarkURL = v
			}
		case "branding.markVersion":
			if v, ok := value.(string); ok {
				document.Branding.MarkVersion = v
			}
		}
		if v, ok := value.(bool); ok {
			document.Features.Flags[key] = v
		}
	}
}

func sectionIDs(definitions []config.RemoteSectionDefinition) []string {
	ids := make([]string, 0, len(definitions))
	for _, definition := range definitions {
		if definition.Enabled {
			ids = append(ids, definition.ID)
		}
	}
	return ids
}

func configVersionHeader(version int64) string {
	return strconv.FormatInt(version, 10)
}