package adminapi

import (
	"crypto/subtle"
	"encoding/json"
	"errors"
	"log/slog"
	"net/http"
	"strings"

	"aigw/internal/adminui"
	"aigw/internal/apierror"
	"aigw/internal/controlplane"

	"github.com/jackc/pgx/v5/pgconn"
)

type API struct {
	store   *controlplane.Store
	manager *controlplane.Manager
	token   []byte
	logger  *slog.Logger
	prefix  string
}

type Options struct {
	Store   *controlplane.Store
	Manager *controlplane.Manager
	Token   string
	Logger  *slog.Logger
	Prefix  string
}

func New(options Options) *API {
	prefix := strings.TrimRight(options.Prefix, "/")
	if prefix == "" {
		prefix = "/admin"
	}
	return &API{store: options.Store, manager: options.Manager, token: []byte(options.Token), logger: options.Logger, prefix: prefix}
}

func (a *API) Handler() http.Handler {
	mux := http.NewServeMux()
	apiPrefix := a.prefix + "/api"
	mux.HandleFunc("GET "+a.prefix, func(w http.ResponseWriter, r *http.Request) {
		http.Redirect(w, r, a.prefix+"/", http.StatusTemporaryRedirect)
	})
	mux.Handle(a.prefix+"/", http.StripPrefix(a.prefix, adminui.Handler()))

	mux.HandleFunc("GET "+apiPrefix+"/overview", a.withAuth(a.overview))
	mux.HandleFunc("GET "+apiPrefix+"/tenants", a.withAuth(a.listTenants))
	mux.HandleFunc("POST "+apiPrefix+"/tenants", a.withAuth(a.createTenant))
	mux.HandleFunc("GET "+apiPrefix+"/projects", a.withAuth(a.listProjects))
	mux.HandleFunc("POST "+apiPrefix+"/projects", a.withAuth(a.createProject))
	mux.HandleFunc("GET "+apiPrefix+"/keys", a.withAuth(a.listKeys))
	mux.HandleFunc("POST "+apiPrefix+"/keys", a.withAuth(a.createKey))
	mux.HandleFunc("POST "+apiPrefix+"/keys/{id}/revoke", a.withAuth(a.revokeKey))
	mux.HandleFunc("GET "+apiPrefix+"/providers", a.withAuth(a.listProviders))
	mux.HandleFunc("POST "+apiPrefix+"/providers", a.withAuth(a.createProvider))
	mux.HandleFunc("POST "+apiPrefix+"/providers/{id}/toggle", a.withAuth(a.toggleProvider))
	mux.HandleFunc("GET "+apiPrefix+"/models", a.withAuth(a.listModels))
	mux.HandleFunc("POST "+apiPrefix+"/models", a.withAuth(a.createModel))
	mux.HandleFunc("POST "+apiPrefix+"/models/{id}/toggle", a.withAuth(a.toggleModel))
	mux.HandleFunc("POST "+apiPrefix+"/reload", a.withAuth(a.reload))
	return mux
}

func (a *API) withAuth(next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		provided := strings.TrimSpace(r.Header.Get("X-Admin-Token"))
		if provided == "" {
			provided = bearerToken(r.Header.Get("Authorization"))
		}
		if len(provided) == 0 || subtle.ConstantTimeCompare([]byte(provided), a.token) != 1 {
			apierror.Write(w, apierror.Error{Status: http.StatusUnauthorized, Type: "admin_unauthorized", Message: "Administrator authentication required"}, requestID(r))
			return
		}
		next(w, r)
	}
}

func (a *API) overview(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.Overview(r.Context())
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	result.RuntimeGeneration = a.manager.Generation()
	result.RedisConfigured = a.manager.RedisConfigured()
	result.RedisConnected = a.manager.RedisConnected()
	writeJSON(w, result)
}

func (a *API) listTenants(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.ListTenants(r.Context())
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) createTenant(w http.ResponseWriter, r *http.Request) {
	var input controlplane.CreateTenantInput
	if !decodeBody(w, r, &input) {
		return
	}
	result, generation, err := a.store.CreateTenant(r.Context(), input)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "tenant", result.ID) {
		return
	}
	writeStatusJSON(w, http.StatusCreated, result)
}

func (a *API) listProjects(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.ListProjects(r.Context())
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) createProject(w http.ResponseWriter, r *http.Request) {
	var input controlplane.CreateProjectInput
	if !decodeBody(w, r, &input) {
		return
	}
	result, generation, err := a.store.CreateProject(r.Context(), input)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "project", result.ID) {
		return
	}
	writeStatusJSON(w, http.StatusCreated, result)
}

func (a *API) listKeys(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.ListAPIKeys(r.Context())
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) createKey(w http.ResponseWriter, r *http.Request) {
	var input controlplane.CreateAPIKeyInput
	if !decodeBody(w, r, &input) {
		return
	}
	result, generation, err := a.store.CreateAPIKey(r.Context(), input)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "api_key", result.ID) {
		return
	}
	writeStatusJSON(w, http.StatusCreated, result)
}

func (a *API) revokeKey(w http.ResponseWriter, r *http.Request) {
	generation, err := a.store.RevokeAPIKey(r.Context(), r.PathValue("id"))
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "api_key", r.PathValue("id")) {
		return
	}
	writeJSON(w, map[string]any{"status": "revoked"})
}

func (a *API) listProviders(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.ListProviders(r.Context())
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) createProvider(w http.ResponseWriter, r *http.Request) {
	var input controlplane.CreateProviderInput
	if !decodeBody(w, r, &input) {
		return
	}
	result, generation, err := a.store.CreateProvider(r.Context(), input)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "provider", result.ID) {
		return
	}
	writeStatusJSON(w, http.StatusCreated, result)
}

func (a *API) toggleProvider(w http.ResponseWriter, r *http.Request) {
	var input struct {
		Enabled bool `json:"enabled"`
	}
	if !decodeBody(w, r, &input) {
		return
	}
	id := r.PathValue("id")
	generation, err := a.store.SetProviderEnabled(r.Context(), id, input.Enabled)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "provider", id) {
		return
	}
	writeJSON(w, map[string]any{"id": id, "enabled": input.Enabled})
}

func (a *API) listModels(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.ListModels(r.Context())
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) createModel(w http.ResponseWriter, r *http.Request) {
	var input controlplane.CreateModelInput
	if !decodeBody(w, r, &input) {
		return
	}
	result, generation, err := a.store.CreateModel(r.Context(), input)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "model", result.ID) {
		return
	}
	writeStatusJSON(w, http.StatusCreated, result)
}

func (a *API) toggleModel(w http.ResponseWriter, r *http.Request) {
	var input struct {
		Enabled bool `json:"enabled"`
	}
	if !decodeBody(w, r, &input) {
		return
	}
	id := r.PathValue("id")
	generation, err := a.store.SetModelEnabled(r.Context(), id, input.Enabled)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "model", id) {
		return
	}
	writeJSON(w, map[string]any{"id": id, "enabled": input.Enabled})
}

func (a *API) reload(w http.ResponseWriter, r *http.Request) {
	generation, err := a.manager.Reload(r.Context())
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, map[string]any{"generation": generation, "status": "reloaded"})
}

func (a *API) changed(w http.ResponseWriter, r *http.Request, generation int64, resource, id string) bool {
	if err := a.manager.AfterMutation(r.Context(), generation, resource, id); err != nil {
		a.logger.Error("admin_control_plane_sync_failed", "resource", resource, "id", id, "error", err)
		apierror.Write(w, apierror.Error{Status: http.StatusServiceUnavailable, Type: "control_plane_sync_failed", Message: "Change was persisted but runtime reload failed; retry reload"}, requestID(r))
		return false
	}
	return true
}

func (a *API) databaseError(w http.ResponseWriter, r *http.Request, err error) {
	a.logger.Error("admin_database_error", "error", err)
	apierror.Write(w, apierror.Error{Status: http.StatusInternalServerError, Type: "control_plane_error", Message: "Control plane unavailable"}, requestID(r))
}

func (a *API) mutationError(w http.ResponseWriter, r *http.Request, err error) {
	status := http.StatusBadRequest
	typeName := "invalid_params"
	message := err.Error()
	if errors.Is(err, controlplane.ErrNotFound) {
		status = http.StatusNotFound
		typeName = "not_found"
		message = "Resource not found"
	}
	var pgError *pgconn.PgError
	if errors.As(err, &pgError) {
		switch pgError.Code {
		case "23505":
			status = http.StatusConflict
			typeName = "already_exists"
			message = "Resource already exists"
		case "23503":
			status = http.StatusBadRequest
			typeName = "invalid_reference"
			message = "Referenced resource does not exist"
		}
	}
	apierror.Write(w, apierror.Error{Status: status, Type: typeName, Message: message}, requestID(r))
}

func decodeBody(w http.ResponseWriter, r *http.Request, destination any) bool {
	r.Body = http.MaxBytesReader(w, r.Body, 1<<20)
	defer r.Body.Close()
	decoder := json.NewDecoder(r.Body)
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(destination); err != nil {
		apierror.Write(w, apierror.Error{Status: http.StatusBadRequest, Type: "invalid_params", Message: "Invalid JSON request body"}, requestID(r))
		return false
	}
	return true
}

func writeJSON(w http.ResponseWriter, value any) {
	writeStatusJSON(w, http.StatusOK, value)
}

func writeStatusJSON(w http.ResponseWriter, status int, value any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}

func bearerToken(header string) string {
	parts := strings.Fields(header)
	if len(parts) == 2 && strings.EqualFold(parts[0], "Bearer") {
		return parts[1]
	}
	return ""
}

func requestID(r *http.Request) string {
	if value := r.Header.Get("X-AIGW-Request-ID"); value != "" {
		return value
	}
	return "admin"
}