package server

import (
	"errors"
	"net/http"

	"galaxy/backend/internal/auth"
	"galaxy/backend/internal/server/handlers"
	"galaxy/backend/internal/server/httperr"
	"galaxy/backend/internal/telemetry"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
	"go.uber.org/zap"
)

// InternalSessionsHandlers groups the gateway-only session handlers
// under `/api/v1/internal/sessions/*`. The current implementation ships real
// implementations; nil *auth.Service falls back to the Stage-3
// placeholder so the contract test continues to validate the OpenAPI
// envelope without booting a database.
type InternalSessionsHandlers struct {
	svc *auth.Service
	logger *zap.Logger
}

// NewInternalSessionsHandlers constructs the handler set. svc may be
// nil — in that case every handler returns 501 not_implemented, matching
// the pre-Stage-5.1 placeholder. logger may also be nil; zap.NewNop is
// used in that case.
func NewInternalSessionsHandlers(svc *auth.Service, logger *zap.Logger) *InternalSessionsHandlers {
	if logger == nil {
		logger = zap.NewNop()
	}
	return &InternalSessionsHandlers{svc: svc, logger: logger.Named("http.internal.sessions")}
}

// Get handles GET /api/v1/internal/sessions/{device_session_id}.
func (h *InternalSessionsHandlers) Get() gin.HandlerFunc {
	if h.svc == nil {
		return handlers.NotImplemented("internalSessionsGet")
	}
	return func(c *gin.Context) {
		deviceSessionID, err := uuid.Parse(c.Param("device_session_id"))
		if err != nil {
			httperr.Abort(c, http.StatusBadRequest, httperr.CodeInvalidRequest, "device_session_id must be a valid UUID")
			return
		}
		ctx := c.Request.Context()
		sess, err := h.svc.GetSession(ctx, deviceSessionID)
		if err != nil {
			if errors.Is(err, auth.ErrSessionNotFound) {
				httperr.Abort(c, http.StatusNotFound, httperr.CodeNotFound, "device session not found")
				return
			}
			h.logger.Error("internal sessions get failed",
				append(telemetry.TraceFieldsFromContext(ctx), zap.Error(err))...,
			)
			httperr.Abort(c, http.StatusInternalServerError, httperr.CodeInternalError, "service error")
			return
		}
		c.JSON(http.StatusOK, deviceSessionToWire(sess))
	}
}

// Revoke handles POST /api/v1/internal/sessions/{device_session_id}/revoke.
func (h *InternalSessionsHandlers) Revoke() gin.HandlerFunc {
	if h.svc == nil {
		return handlers.NotImplemented("internalSessionsRevoke")
	}
	return func(c *gin.Context) {
		deviceSessionID, err := uuid.Parse(c.Param("device_session_id"))
		if err != nil {
			httperr.Abort(c, http.StatusBadRequest, httperr.CodeInvalidRequest, "device_session_id must be a valid UUID")
			return
		}
		ctx := c.Request.Context()
		sess, err := h.svc.RevokeSession(ctx, deviceSessionID)
		if err != nil {
			if errors.Is(err, auth.ErrSessionNotFound) {
				httperr.Abort(c, http.StatusNotFound, httperr.CodeNotFound, "device session not found")
				return
			}
			h.logger.Error("internal sessions revoke failed",
				append(telemetry.TraceFieldsFromContext(ctx), zap.Error(err))...,
			)
			httperr.Abort(c, http.StatusInternalServerError, httperr.CodeInternalError, "service error")
			return
		}
		c.JSON(http.StatusOK, deviceSessionToWire(sess))
	}
}

// RevokeAllForUser handles POST /api/v1/internal/sessions/users/{user_id}/revoke-all.
func (h *InternalSessionsHandlers) RevokeAllForUser() gin.HandlerFunc {
	if h.svc == nil {
		return handlers.NotImplemented("internalSessionsRevokeAllForUser")
	}
	return func(c *gin.Context) {
		userID, err := uuid.Parse(c.Param("user_id"))
		if err != nil {
			httperr.Abort(c, http.StatusBadRequest, httperr.CodeInvalidRequest, "user_id must be a valid UUID")
			return
		}
		ctx := c.Request.Context()
		revoked, err := h.svc.RevokeAllForUser(ctx, userID)
		if err != nil {
			h.logger.Error("internal sessions revoke-all failed",
				append(telemetry.TraceFieldsFromContext(ctx), zap.Error(err))...,
			)
			httperr.Abort(c, http.StatusInternalServerError, httperr.CodeInternalError, "service error")
			return
		}
		c.JSON(http.StatusOK, gin.H{
			"user_id": userID.String(),
			"revoked_count": len(revoked),
		})
	}
}