package adminapi

import (
	"context"
	"crypto/rand"
	"crypto/subtle"
	"encoding/hex"
	"encoding/json"
	"errors"
	"log/slog"
	"net"
	"net/http"
	"strings"
	"time"

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

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

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

type actorKey struct{}
type auditWriter struct {
	http.ResponseWriter
	status int
}

func (w *auditWriter) WriteHeader(status int) {
	w.status = status
	w.ResponseWriter.WriteHeader(status)
}
func (w *auditWriter) Write(body []byte) (int, error) {
	if w.status == 0 {
		w.status = http.StatusOK
	}
	return w.ResponseWriter.Write(body)
}

type Options struct {
	Store   *controlplane.Store
	Manager *controlplane.Manager
	Billing *billing.Service
	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, billing: options.Billing, 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("overview.read", a.overview))
	mux.HandleFunc("GET "+apiPrefix+"/tenants", a.withAuth("tenants.read", a.listTenants))
	mux.HandleFunc("POST "+apiPrefix+"/tenants", a.withAuth("tenants.write", a.createTenant))
	mux.HandleFunc("GET "+apiPrefix+"/projects", a.withAuth("projects.read", a.listProjects))
	mux.HandleFunc("POST "+apiPrefix+"/projects", a.withAuth("projects.write", a.createProject))
	mux.HandleFunc("GET "+apiPrefix+"/keys", a.withAuth("keys.read", a.listKeys))
	mux.HandleFunc("POST "+apiPrefix+"/keys", a.withAuth("keys.write", a.createKey))
	mux.HandleFunc("POST "+apiPrefix+"/keys/{id}/revoke", a.withAuth("keys.write", a.revokeKey))
	mux.HandleFunc("GET "+apiPrefix+"/providers", a.withAuth("platform.read", a.listProviders))
	mux.HandleFunc("POST "+apiPrefix+"/providers", a.withAuth("platform.write", a.createProvider))
	mux.HandleFunc("POST "+apiPrefix+"/providers/{id}/toggle", a.withAuth("platform.write", a.toggleProvider))
	mux.HandleFunc("GET "+apiPrefix+"/models", a.withAuth("platform.read", a.listModels))
	mux.HandleFunc("POST "+apiPrefix+"/models", a.withAuth("platform.write", a.createModel))
	mux.HandleFunc("POST "+apiPrefix+"/models/{id}/toggle", a.withAuth("platform.write", a.toggleModel))
	mux.HandleFunc("POST "+apiPrefix+"/reload", a.withAuth("platform.write", a.reload))
	if a.billing != nil {
		mux.HandleFunc("GET "+apiPrefix+"/billing/accounts", a.withAuth("billing.read", a.listBillingAccounts))
		mux.HandleFunc("GET "+apiPrefix+"/billing/ledger", a.withAuth("billing.read", a.listBillingLedger))
		mux.HandleFunc("POST "+apiPrefix+"/billing/adjustments", a.withAuth("billing.adjust", a.adjustBalance))
		mux.HandleFunc("POST "+apiPrefix+"/billing/checkout-sessions", a.withAuth("billing.topup", a.createCheckoutSession))
	}
	mux.HandleFunc("GET "+apiPrefix+"/usage", a.withAuth("usage.read", a.listUsage))
	mux.HandleFunc("GET "+apiPrefix+"/usage/summary", a.withAuth("usage.read", a.usageSummary))
	mux.HandleFunc("GET "+apiPrefix+"/limits", a.withAuth("limits.read", a.listLimits))
	mux.HandleFunc("POST "+apiPrefix+"/limits/{project_id}", a.withAuth("limits.write", a.setLimit))
	mux.HandleFunc("GET "+apiPrefix+"/users", a.withAuth("users.read", a.listUsers))
	mux.HandleFunc("POST "+apiPrefix+"/users", a.withAuth("users.write", a.createUser))
	mux.HandleFunc("POST "+apiPrefix+"/users/{id}/revoke", a.withAuth("users.write", a.revokeUser))
	mux.HandleFunc("GET "+apiPrefix+"/audit", a.withAuth("audit.read", a.listAudit))
	mux.HandleFunc("GET "+apiPrefix+"/me", a.withAuth("overview.read", a.me))
	return mux
}

func (a *API) withAuth(permission string, next http.HandlerFunc) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Header.Get("X-AIGW-Request-ID") == "" {
			r.Header.Set("X-AIGW-Request-ID", adminRequestID(r))
		}
		w.Header().Set("X-AIGW-Request-ID", r.Header.Get("X-AIGW-Request-ID"))
		provided := strings.TrimSpace(r.Header.Get("X-Admin-Token"))
		if provided == "" {
			provided = bearerToken(r.Header.Get("Authorization"))
		}
		actor := controlplane.ConsoleActor{}
		if len(provided) > 0 && len(a.token) > 0 && subtle.ConstantTimeCompare([]byte(provided), a.token) == 1 {
			actor = controlplane.ConsoleActor{Role: controlplane.RolePlatformAdmin, DisplayName: "Bootstrap administrator", Bootstrap: true}
		} else if provided != "" && a.store != nil {
			var err error
			actor, err = a.store.AuthenticateConsoleToken(r.Context(), provided)
			if err != nil && !errors.Is(err, controlplane.ErrConsoleUnauthorized) {
				a.logger.Error("console_authentication_failed", "error", err)
				apierror.Write(w, apierror.Error{Status: http.StatusServiceUnavailable, Type: "control_plane_unavailable", Message: "Control plane authentication is temporarily unavailable"}, requestID(r))
				return
			}
			if err != nil {
				actor = controlplane.ConsoleActor{}
			}
		}
		if actor.Role == "" {
			apierror.Write(w, apierror.Error{Status: http.StatusUnauthorized, Type: "admin_unauthorized", Message: "Administrator authentication required"}, requestID(r))
			return
		}
		if !actor.Can(permission) {
			aw := &auditWriter{ResponseWriter: w}
			apierror.Write(aw, apierror.Error{Status: http.StatusForbidden, Type: "admin_forbidden", Message: "You do not have permission for this operation"}, requestID(r))
			a.writeAudit(r, actor, permission, aw.status)
			return
		}
		request := r.WithContext(context.WithValue(r.Context(), actorKey{}, actor))
		aw := &auditWriter{ResponseWriter: w}
		next(aw, request)
		if aw.status == 0 {
			aw.status = http.StatusOK
		}
		a.writeAudit(request, actor, permission, aw.status)
	}
}

func (a *API) actor(r *http.Request) controlplane.ConsoleActor {
	actor, _ := r.Context().Value(actorKey{}).(controlplane.ConsoleActor)
	return actor
}

func (a *API) writeAudit(r *http.Request, actor controlplane.ConsoleActor, action string, status int) {
	if a.store == nil {
		return
	}
	ip := r.RemoteAddr
	if host, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
		ip = host
	}
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	if err := a.store.WriteAudit(ctx, controlplane.AuditInput{Actor: actor, RequestID: requestID(r), Method: r.Method, Path: r.URL.Path, Action: action, StatusCode: status, RemoteIP: ip, UserAgent: r.UserAgent()}); err != nil && a.logger != nil {
		a.logger.Warn("admin_audit_write_failed", "error", err)
	}
}

func adminRequestID(r *http.Request) string {
	if id := r.Header.Get("X-AIGW-Request-ID"); id != "" {
		return id
	}
	var b [12]byte
	if _, err := rand.Read(b[:]); err == nil {
		return "adm_" + hex.EncodeToString(b[:])
	}
	return "adm_unknown"
}

func (a *API) overview(w http.ResponseWriter, r *http.Request) {
	actor := a.actor(r)
	tenantID := actor.TenantID
	result, err := a.store.OverviewFor(r.Context(), tenantID)
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	result.RuntimeGeneration = a.manager.Generation()
	result.RedisConfigured = a.manager.RedisConfigured()
	result.RedisConnected = a.manager.RedisConnected()
	result.BillingEnabled = a.billing != nil
	if a.billing != nil {
		result.StripeEnabled = a.billing.StripeEnabled()
		result.BillingCurrency = a.billing.Currency()
	}
	writeJSON(w, result)
}

func (a *API) listBillingAccounts(w http.ResponseWriter, r *http.Request) {
	result, err := a.billing.ListAccounts(r.Context(), a.actor(r).TenantID)
	if err != nil {
		a.billingError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) listBillingLedger(w http.ResponseWriter, r *http.Request) {
	tenantID := a.actor(r).TenantID
	if tenantID == "" {
		tenantID = r.URL.Query().Get("tenant_id")
	}
	result, err := a.billing.ListLedger(r.Context(), tenantID, 200)
	if err != nil {
		a.billingError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) adjustBalance(w http.ResponseWriter, r *http.Request) {
	var input billing.AdjustmentInput
	if !decodeBody(w, r, &input) {
		return
	}
	result, err := a.billing.AdjustBalance(r.Context(), input)
	if err != nil {
		a.billingError(w, r, err)
		return
	}
	writeStatusJSON(w, http.StatusCreated, result)
}

func (a *API) createCheckoutSession(w http.ResponseWriter, r *http.Request) {
	var input billing.CheckoutInput
	if !decodeBody(w, r, &input) {
		return
	}
	if tenantID := a.actor(r).TenantID; tenantID != "" {
		input.TenantID = tenantID
	}
	result, err := a.billing.CreateCheckout(r.Context(), input)
	if err != nil {
		a.billingError(w, r, err)
		return
	}
	writeStatusJSON(w, http.StatusCreated, result)
}

func (a *API) listTenants(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.ListTenantsFor(r.Context(), a.actor(r).TenantID)
	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.ListProjectsFor(r.Context(), a.actor(r).TenantID)
	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
	}
	if tenantID := a.actor(r).TenantID; tenantID != "" {
		input.TenantID = tenantID
	}
	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.ListAPIKeysFor(r.Context(), a.actor(r).TenantID)
	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
	}
	if tenantID := a.actor(r).TenantID; tenantID != "" {
		input.TenantID = tenantID
	}
	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) {
	if err := a.requireResourceTenant(r, "api_key", r.PathValue("id")); err != nil {
		a.scopeError(w, r)
		return
	}
	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) listUsage(w http.ResponseWriter, r *http.Request) {
	query := controlplane.UsageQuery{TenantID: a.actor(r).TenantID, ProjectID: r.URL.Query().Get("project_id"), Model: r.URL.Query().Get("model"), Limit: 200}
	result, err := a.store.ListUsage(r.Context(), query)
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) usageSummary(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.UsageSummary(r.Context(), a.actor(r).TenantID, r.URL.Query().Get("project_id"))
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, result)
}

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

func (a *API) setLimit(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("project_id")
	if err := a.requireResourceTenant(r, "project", id); err != nil {
		a.scopeError(w, r)
		return
	}
	var input controlplane.SetProjectLimitInput
	if !decodeBody(w, r, &input) {
		return
	}
	result, generation, err := a.store.SetProjectLimit(r.Context(), id, input)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	if !a.changed(w, r, generation, "project_limit", id) {
		return
	}
	writeJSON(w, result)
}

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

func (a *API) createUser(w http.ResponseWriter, r *http.Request) {
	var input controlplane.CreateConsoleUserInput
	if !decodeBody(w, r, &input) {
		return
	}
	if tenantID := a.actor(r).TenantID; tenantID != "" {
		input.TenantID = tenantID
		if strings.HasPrefix(input.Role, "platform_") {
			a.scopeError(w, r)
			return
		}
	}
	result, err := a.store.CreateConsoleUser(r.Context(), input)
	if err != nil {
		a.mutationError(w, r, err)
		return
	}
	writeStatusJSON(w, http.StatusCreated, result)
}

func (a *API) revokeUser(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	if err := a.requireResourceTenant(r, "console_user", id); err != nil {
		a.scopeError(w, r)
		return
	}
	if err := a.store.RevokeConsoleUser(r.Context(), id, a.actor(r).TenantID); err != nil {
		a.mutationError(w, r, err)
		return
	}
	writeJSON(w, map[string]any{"status": "revoked", "id": id})
}

func (a *API) listAudit(w http.ResponseWriter, r *http.Request) {
	result, err := a.store.ListAudit(r.Context(), a.actor(r).TenantID, 200)
	if err != nil {
		a.databaseError(w, r, err)
		return
	}
	writeJSON(w, result)
}

func (a *API) me(w http.ResponseWriter, r *http.Request) {
	actor := a.actor(r)
	writeJSON(w, map[string]any{"actor": actor, "permissions": actor.Permissions()})
}

func (a *API) requireResourceTenant(r *http.Request, resource, id string) error {
	actor := a.actor(r)
	if actor.IsPlatform() {
		return nil
	}
	tenantID, err := a.store.ResourceTenantID(r.Context(), resource, id)
	if err != nil || tenantID == "" || tenantID != actor.TenantID {
		return errors.New("resource is outside tenant scope")
	}
	return nil
}

func (a *API) scopeError(w http.ResponseWriter, r *http.Request) {
	apierror.Write(w, apierror.Error{Status: http.StatusForbidden, Type: "tenant_scope", Message: "Resource is outside your tenant"}, requestID(r))
}

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 (a *API) billingError(w http.ResponseWriter, r *http.Request, err error) {
	status := http.StatusInternalServerError
	typeName := "billing_error"
	message := "Billing operation failed"
	switch {
	case errors.Is(err, billing.ErrInvalidAmount):
		status = http.StatusBadRequest
		typeName = "invalid_amount"
		message = "Amount is outside the configured bounds"
	case errors.Is(err, billing.ErrInsufficientBalance):
		status = http.StatusPaymentRequired
		typeName = "insufficient_balance"
		message = "Available balance is insufficient"
	case errors.Is(err, billing.ErrStripeDisabled):
		status = http.StatusServiceUnavailable
		typeName = "stripe_disabled"
		message = "Stripe top-ups are disabled"
	default:
		a.logger.Error("admin_billing_error", "error", err)
	}
	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 adminRequestID(r)
}