package database

import (
	"database/sql"
	"fmt"
	"github.com/google/uuid"
	"relay-server/model"
	"relay-server/utils"
)

func CreateGroup(db *sql.DB, groupName string, userID uuid.UUID) (uuid.UUID, error) {
	createConversationQuery := `
  	  INSERT INTO Conversations (conversation_type, name)
  	  VALUES ('group', $1)
  	  RETURNING conversation_id AS group_id;
  	`

	insertGroupAdminQuery := `
  	  INSERT INTO GroupAdmins (conversation_id, user_id, granted_by, is_owner)
  	  VALUES ($1, $2, $3, true)
  	  RETURNING granted_at;
  	`

	// Create conversation
	var groupID uuid.UUID
	err := db.QueryRow(createConversationQuery, groupName).Scan(&groupID)
	if err != nil {
		return uuid.Nil, utils.NewError(utils.ErrInternal, "Failed to create group", fmt.Errorf("failed to create group: %w", err))
	}

	// Insert group admin (make user that created the group an admin)
	var grantedAt string
	err = db.QueryRow(insertGroupAdminQuery, groupID, userID, userID).Scan(&grantedAt)
	if err != nil {
		return uuid.Nil, utils.NewError(utils.ErrInternal, "Failed to create group", fmt.Errorf("failed to insert group admin: %w", err))
	}

	// Add self as group member
	_, err = AddMemberToGroup(db, userID, groupID)
	if err != nil {
		return uuid.Nil, err
	}

	// Insert group contact
	_, err = InsertContactByID(db, userID, groupID)
	if err != nil {
		return groupID, utils.NewError(utils.ErrInternal, "Failed to create group contact", fmt.Errorf("failed to insert group contact: %w", err))
	}

	return groupID, nil
}

func AddMemberToGroup(db *sql.DB, userID uuid.UUID, groupID uuid.UUID) (uuid.UUID, error) {
	query := `
  	  INSERT INTO Memberships (conversation_id, user_id)
  	  VALUES ($1, $2)
  	  ON CONFLICT DO NOTHING
  	  RETURNING user_id;
  	`
	var memberID uuid.UUID
	err := db.QueryRow(query, groupID, userID).Scan(&memberID)
	if err != nil {
		return uuid.Nil, utils.NewError(utils.ErrInternal, "Failed to add member to group", fmt.Errorf("failed to add member to group: %w", err))
	}
	return memberID, nil
}

func GetMembers(db *sql.DB, groupID uuid.UUID) ([]*model.Member, error) {
	query := `
		SELECT 
			a.user_id,
			a.username,
			CASE
				WHEN ga.user_id IS NOT NULL THEN TRUE
				ELSE FALSE
			END AS isAdmin,
			COALESCE(ga.is_owner, FALSE) AS isOwner
		FROM Memberships m
		JOIN Accounts a ON m.user_id = a.user_id
		LEFT JOIN GroupAdmins ga ON m.user_id = ga.user_id AND m.conversation_id = ga.conversation_id
		WHERE m.conversation_id = $1;
	`

	rows, err := db.Query(query, groupID)
	if err != nil {
		return []*model.Member{}, utils.NewError(utils.ErrInternal, "Failed to get members", fmt.Errorf("failed to get members: %w", err))
	}
	defer rows.Close()

	var members []*model.Member
	for rows.Next() {
		var member model.Member
		err = rows.Scan(&member.UserID, &member.Username, &member.IsAdmin, &member.IsOwner)
		if err != nil {
			return []*model.Member{}, utils.NewError(utils.ErrInternal, "Failed to get members", fmt.Errorf("failed to scan member: %w", err))
		}
		members = append(members, &member)
	}

	if err = rows.Err(); err != nil {
		return []*model.Member{}, utils.NewError(utils.ErrInternal, "Failed to get members", fmt.Errorf("error iterating members: %w", err))
	}

	return members, nil
}

func IsAdmin(db *sql.DB, userID uuid.UUID, conversationID uuid.UUID) (bool, error) {
	query := `
  	  SELECT COUNT(1) FROM GroupAdmins
  	  WHERE user_id = $1
  	  AND conversation_id = $2;
  	`
	var count int
	err := db.QueryRow(query, userID, conversationID).Scan(&count)
	if err != nil {
		return false, utils.NewError(utils.ErrInternal, "Failed to check admin status", fmt.Errorf("failed to check admin status: %w", err))
	}
	return count > 0, nil
}

func IsMember(db *sql.DB, userID uuid.UUID, conversationID uuid.UUID) (bool, error) {
	query := `
  	  SELECT COUNT(1) FROM Memberships
  	  WHERE user_id = $1
  	  AND conversation_id = $2;
  	`
	var count int
	err := db.QueryRow(query, userID, conversationID).Scan(&count)
	if err != nil {
		return false, utils.NewError(utils.ErrInternal, "Failed to check membership", fmt.Errorf("failed to check membership: %w", err))
	}
	return count > 0, nil
}

func GetUserConversations(db *sql.DB, userID string) ([]string, error) {
	query := `
  	  SELECT DISTINCT m.conversation_id
  	  FROM Memberships m
  	  JOIN Conversations c ON m.conversation_id = c.conversation_id
  	  WHERE m.user_id = $1 
  	  AND c.conversation_type = 'group';
  	`

	var conversations []string

	rows, err := db.Query(query, userID)
	if err != nil {
		return []string{}, fmt.Errorf("failed to get user conversations: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var conversationID string
		err = rows.Scan(&conversationID)
		if err != nil {
			return []string{}, fmt.Errorf("failed to scan conversation: %w", err)
		}
		conversations = append(conversations, conversationID)
	}
	if err := rows.Err(); err != nil {
		return []string{}, fmt.Errorf("error iterating conversations: %w", err)
	}

	return conversations, nil
}

func RemoveUserFromGroup(db *sql.DB, userID uuid.UUID, groupID uuid.UUID) (string, error) {
	removeUserFromGroupQuery := `
  	  DELETE FROM Memberships 
  	  WHERE conversation_id = $1 AND user_id = $2;
  	`

	isOwner, err := IsGroupOwner(db, userID, groupID)
	if err != nil {
		return "Failed to remove user from group", fmt.Errorf("failed to check if user is group owner: %w", err)
	}
	if !isOwner {
		return "Cannot remove group owner", nil
	}
	res, err := db.Exec(removeUserFromGroupQuery, groupID, userID)
	if err != nil {
		return "Failed to remove user from group", fmt.Errorf("failed to remove user from group: %w", err)
	}
	rowsAffected, err := res.RowsAffected()
	if err != nil {
		return "Failed to remove user from group", fmt.Errorf("failed to get rows affected: %w", err)
	}
	if rowsAffected == 0 {
		return "User is not a member of the group", nil
	}
	return "Successfully removed user from group", nil
}

func IsGroupOwner(db *sql.DB, userID uuid.UUID, groupID uuid.UUID) (bool, error) {
	query := `
    SELECT EXISTS (
      SELECT 1 FROM GroupAdmins
      WHERE conversation_id = $1
      AND user_id = $2
      AND is_owner = true
    ) AS is_owner;
  `
	var isOwner bool
	err := db.QueryRow(query, groupID, userID).Scan(&isOwner)
	if err != nil {
		return false, fmt.Errorf("failed to check if user is group owner: %w", err)
	}
	return isOwner, nil
}