//go:build linux && cgo && !agent

package db

import (
	"context"
	"errors"
	"fmt"
	"net/http"

	"github.com/canonical/go-dqlite/v3/client"

	"github.com/canonical/lxd/lxd/db/query"
	"github.com/canonical/lxd/shared/api"
)

// RaftNode holds information about a single node in the dqlite raft cluster.
//
// This is just a convenience alias for the equivalent data structure in the
// dqlite client package.
type RaftNode struct {
	client.NodeInfo
	Name string `yaml:"name"`
}

// RaftRole captures the role of dqlite/raft node.
type RaftRole = client.NodeRole

// RaftNode roles.
const (
	RaftVoter   = client.Voter
	RaftStandBy = client.StandBy
	RaftSpare   = client.Spare
)

// GetRaftNodes returns information about all LXD nodes that are members of the
// dqlite Raft cluster (possibly including the local member). If this LXD
// instance is not running in clustered mode, an empty list is returned.
func (n *NodeTx) GetRaftNodes(ctx context.Context) ([]RaftNode, error) {
	nodes := []RaftNode{}

	sql := "SELECT id, address, role, name FROM raft_nodes ORDER BY id"
	err := query.Scan(ctx, n.tx, sql, func(scan func(dest ...any) error) error {
		node := RaftNode{}
		err := scan(&node.ID, &node.Address, &node.Role, &node.Name)
		if err != nil {
			return err
		}

		nodes = append(nodes, node)

		return nil
	})
	if err != nil {
		return nil, fmt.Errorf("Failed to fetch raft nodes: %w", err)
	}

	return nodes, nil
}

// GetRaftNodeAddresses returns the addresses of all LXD nodes that are members of
// the dqlite Raft cluster (possibly including the local member). If this LXD
// instance is not running in clustered mode, an empty list is returned.
func (n *NodeTx) GetRaftNodeAddresses(ctx context.Context) ([]string, error) {
	return query.SelectStrings(ctx, n.tx, "SELECT address FROM raft_nodes")
}

// GetRaftNodeAddress returns the address of the LXD raft node with the given ID,
// if any matching row exists.
func (n *NodeTx) GetRaftNodeAddress(ctx context.Context, id int64) (string, error) {
	stmt := "SELECT address FROM raft_nodes WHERE id=?"
	addresses, err := query.SelectStrings(ctx, n.tx, stmt, id)
	if err != nil {
		return "", err
	}

	switch len(addresses) {
	case 0:
		return "", api.StatusErrorf(http.StatusNotFound, "Raft member not found")
	case 1:
		return addresses[0], nil
	default:
		// This should never happen since we have a UNIQUE constraint
		// on the raft_nodes.id column.
		return "", errors.New("more than one match found")
	}
}

// CreateFirstRaftNode adds a the first node of the cluster. It ensures that the
// database ID is 1, to match the server ID of the first raft log entry.
//
// This method is supposed to be called when there are no rows in raft_nodes,
// and it will replace whatever existing row has ID 1.
func (n *NodeTx) CreateFirstRaftNode(address string, name string) error {
	columns := []string{"id", "address", "name"}
	values := []any{int64(1), address, name}
	id, err := query.UpsertObject(n.tx, "raft_nodes", columns, values)
	if err != nil {
		return err
	}

	if id != 1 {
		return errors.New("could not set raft node ID to 1")
	}

	return nil
}

// CreateRaftNode adds a node to the current list of LXD nodes that are part of the
// dqlite Raft cluster. It returns the ID of the newly inserted row.
func (n *NodeTx) CreateRaftNode(address string, name string) (int64, error) {
	columns := []string{"address", "name"}
	values := []any{address, name}
	return query.UpsertObject(n.tx, "raft_nodes", columns, values)
}

// RemoveRaftNode removes a node from the current list of LXD nodes that are
// part of the dqlite Raft cluster.
func (n *NodeTx) RemoveRaftNode(id int64) error {
	deleted, err := query.DeleteObject(n.tx, "raft_nodes", id)
	if err != nil {
		return err
	}

	if !deleted {
		return api.StatusErrorf(http.StatusNotFound, "Raft member not found")
	}

	return nil
}

// ReplaceRaftNodes replaces the current list of raft nodes.
func (n *NodeTx) ReplaceRaftNodes(nodes []RaftNode) error {
	_, err := n.tx.Exec("DELETE FROM raft_nodes")
	if err != nil {
		return err
	}

	columns := []string{"id", "address", "role", "name"}
	for _, node := range nodes {
		values := []any{node.ID, node.Address, node.Role, node.Name}
		_, err := query.UpsertObject(n.tx, "raft_nodes", columns, values)
		if err != nil {
			return err
		}
	}
	return nil
}
