package grpcserver

import (
	"context"
	"errors"
	"fmt"
	"strconv"

	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"

	pb "git.wntrmute.dev/kyle/mcr/gen/mcr/v1"
	"git.wntrmute.dev/kyle/mcr/internal/auth"
	"git.wntrmute.dev/kyle/mcr/internal/db"
	"git.wntrmute.dev/kyle/mcr/internal/policy"
)

var validActions = map[string]bool{
	string(policy.ActionVersionCheck): true,
	string(policy.ActionPull):         true,
	string(policy.ActionPush):         true,
	string(policy.ActionDelete):       true,
	string(policy.ActionCatalog):      true,
	string(policy.ActionPolicyManage): true,
}

// policyService implements pb.PolicyServiceServer.
type policyService struct {
	pb.UnimplementedPolicyServiceServer
	db      *db.DB
	engine  PolicyReloader
	auditFn AuditFunc
}

func (s *policyService) ListPolicyRules(_ context.Context, req *pb.ListPolicyRulesRequest) (*pb.ListPolicyRulesResponse, error) {
	limit := int32(50)
	offset := int32(0)
	if req.GetPagination() != nil {
		if req.Pagination.Limit > 0 {
			limit = req.Pagination.Limit
		}
		if req.Pagination.Offset >= 0 {
			offset = req.Pagination.Offset
		}
	}

	rules, err := s.db.ListPolicyRules(int(limit), int(offset))
	if err != nil {
		return nil, status.Errorf(codes.Internal, "internal error")
	}

	var result []*pb.PolicyRule
	for _, r := range rules {
		result = append(result, policyRuleRowToProto(&r))
	}

	return &pb.ListPolicyRulesResponse{Rules: result}, nil
}

func (s *policyService) CreatePolicyRule(ctx context.Context, req *pb.CreatePolicyRuleRequest) (*pb.PolicyRule, error) {
	if req.GetPriority() < 1 {
		return nil, status.Errorf(codes.InvalidArgument, "priority must be >= 1 (0 is reserved for built-ins)")
	}
	if req.GetDescription() == "" {
		return nil, status.Errorf(codes.InvalidArgument, "description is required")
	}
	if err := validateEffect(req.GetEffect()); err != nil {
		return nil, status.Errorf(codes.InvalidArgument, "%s", err.Error())
	}
	if len(req.GetActions()) == 0 {
		return nil, status.Errorf(codes.InvalidArgument, "at least one action is required")
	}
	if err := validateActions(req.GetActions()); err != nil {
		return nil, status.Errorf(codes.InvalidArgument, "%s", err.Error())
	}

	claims := auth.ClaimsFromContext(ctx)
	createdBy := ""
	if claims != nil {
		createdBy = claims.Subject
	}

	row := db.PolicyRuleRow{
		Priority:     int(req.Priority),
		Description:  req.Description,
		Effect:       req.Effect,
		Roles:        req.Roles,
		AccountTypes: req.AccountTypes,
		SubjectUUID:  req.SubjectUuid,
		Actions:      req.Actions,
		Repositories: req.Repositories,
		Enabled:      req.Enabled,
		CreatedBy:    createdBy,
	}

	id, err := s.db.CreatePolicyRule(row)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "internal error")
	}

	// Reload policy engine.
	if s.engine != nil {
		_ = s.engine.Reload(s.db)
	}

	if s.auditFn != nil {
		s.auditFn("policy_rule_created", createdBy, "", "", "", map[string]string{
			"rule_id": strconv.FormatInt(id, 10),
		})
	}

	created, err := s.db.GetPolicyRule(id)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "internal error")
	}

	return policyRuleRowToProto(created), nil
}

func (s *policyService) GetPolicyRule(_ context.Context, req *pb.GetPolicyRuleRequest) (*pb.PolicyRule, error) {
	if req.GetId() == 0 {
		return nil, status.Errorf(codes.InvalidArgument, "rule ID required")
	}

	rule, err := s.db.GetPolicyRule(req.Id)
	if err != nil {
		if errors.Is(err, db.ErrPolicyRuleNotFound) {
			return nil, status.Errorf(codes.NotFound, "policy rule not found")
		}
		return nil, status.Errorf(codes.Internal, "internal error")
	}

	return policyRuleRowToProto(rule), nil
}

func (s *policyService) UpdatePolicyRule(ctx context.Context, req *pb.UpdatePolicyRuleRequest) (*pb.PolicyRule, error) {
	if req.GetId() == 0 {
		return nil, status.Errorf(codes.InvalidArgument, "rule ID required")
	}

	mask := make(map[string]bool, len(req.GetUpdateMask()))
	for _, f := range req.GetUpdateMask() {
		mask[f] = true
	}

	// Validate fields if they are in the update mask.
	if mask["priority"] && req.Priority < 1 {
		return nil, status.Errorf(codes.InvalidArgument, "priority must be >= 1 (0 is reserved for built-ins)")
	}
	if mask["effect"] {
		if err := validateEffect(req.GetEffect()); err != nil {
			return nil, status.Errorf(codes.InvalidArgument, "%s", err.Error())
		}
	}
	if mask["actions"] {
		if len(req.GetActions()) == 0 {
			return nil, status.Errorf(codes.InvalidArgument, "at least one action is required")
		}
		if err := validateActions(req.GetActions()); err != nil {
			return nil, status.Errorf(codes.InvalidArgument, "%s", err.Error())
		}
	}

	updates := db.PolicyRuleRow{}
	if mask["priority"] {
		updates.Priority = int(req.Priority)
	}
	if mask["description"] {
		updates.Description = req.Description
	}
	if mask["effect"] {
		updates.Effect = req.Effect
	}
	if mask["roles"] {
		updates.Roles = req.Roles
	}
	if mask["account_types"] {
		updates.AccountTypes = req.AccountTypes
	}
	if mask["subject_uuid"] {
		updates.SubjectUUID = req.SubjectUuid
	}
	if mask["actions"] {
		updates.Actions = req.Actions
	}
	if mask["repositories"] {
		updates.Repositories = req.Repositories
	}

	if err := s.db.UpdatePolicyRule(req.Id, updates); err != nil {
		if errors.Is(err, db.ErrPolicyRuleNotFound) {
			return nil, status.Errorf(codes.NotFound, "policy rule not found")
		}
		return nil, status.Errorf(codes.Internal, "internal error")
	}

	// Handle enabled separately since it's a bool.
	if mask["enabled"] {
		if err := s.db.SetPolicyRuleEnabled(req.Id, req.Enabled); err != nil {
			return nil, status.Errorf(codes.Internal, "internal error")
		}
	}

	// Reload policy engine.
	if s.engine != nil {
		_ = s.engine.Reload(s.db)
	}

	if s.auditFn != nil {
		claims := auth.ClaimsFromContext(ctx)
		actorID := ""
		if claims != nil {
			actorID = claims.Subject
		}
		s.auditFn("policy_rule_updated", actorID, "", "", "", map[string]string{
			"rule_id": strconv.FormatInt(req.Id, 10),
		})
	}

	updated, err := s.db.GetPolicyRule(req.Id)
	if err != nil {
		return nil, status.Errorf(codes.Internal, "internal error")
	}

	return policyRuleRowToProto(updated), nil
}

func (s *policyService) DeletePolicyRule(ctx context.Context, req *pb.DeletePolicyRuleRequest) (*pb.DeletePolicyRuleResponse, error) {
	if req.GetId() == 0 {
		return nil, status.Errorf(codes.InvalidArgument, "rule ID required")
	}

	if err := s.db.DeletePolicyRule(req.Id); err != nil {
		if errors.Is(err, db.ErrPolicyRuleNotFound) {
			return nil, status.Errorf(codes.NotFound, "policy rule not found")
		}
		return nil, status.Errorf(codes.Internal, "internal error")
	}

	// Reload policy engine.
	if s.engine != nil {
		_ = s.engine.Reload(s.db)
	}

	if s.auditFn != nil {
		claims := auth.ClaimsFromContext(ctx)
		actorID := ""
		if claims != nil {
			actorID = claims.Subject
		}
		s.auditFn("policy_rule_deleted", actorID, "", "", "", map[string]string{
			"rule_id": strconv.FormatInt(req.Id, 10),
		})
	}

	return &pb.DeletePolicyRuleResponse{}, nil
}

// policyRuleRowToProto converts a db.PolicyRuleRow to a protobuf PolicyRule.
func policyRuleRowToProto(r *db.PolicyRuleRow) *pb.PolicyRule {
	return &pb.PolicyRule{
		Id:           r.ID,
		Priority:     int32(r.Priority), //nolint:gosec // priority is always small positive int
		Description:  r.Description,
		Effect:       r.Effect,
		Roles:        r.Roles,
		AccountTypes: r.AccountTypes,
		SubjectUuid:  r.SubjectUUID,
		Actions:      r.Actions,
		Repositories: r.Repositories,
		Enabled:      r.Enabled,
		CreatedBy:    r.CreatedBy,
		CreatedAt:    r.CreatedAt,
		UpdatedAt:    r.UpdatedAt,
	}
}

func validateEffect(effect string) error {
	if effect != "allow" && effect != "deny" {
		return fmt.Errorf("invalid effect: %q (must be 'allow' or 'deny')", effect)
	}
	return nil
}

func validateActions(actions []string) error {
	for _, a := range actions {
		if !validActions[a] {
			return fmt.Errorf("invalid action: %q", a)
		}
	}
	return nil
}