package synchronizator

import (
	"context"
	"encoding/json"
	"fmt"
	"slices"
	"strings"
)

type default_collection struct {
	platform_name string
}

func (collection *default_collection) GetClass() string {
	platform_name := strings.ToUpper(collection.platform_name)
	return platform_name + "_DEFAULT"
}

func (collection *default_collection) GetMetadata() []byte {
	return nil
}

func (collection *default_collection) FromNode(_class string, name string, metadata []byte) error {
	if _class != "DEFAULT" {
		return fmt.Errorf("invalid class %s", _class)
	}
	return nil
}

// Utility struct to represent a collection of nodes, it's a [Node] itself so all
// the node's functionality is available.
type Collection struct {
	Node               // Underlaying node info
	childs     []*Node // Child nodes
	is_default bool
}

func (collection *Collection) loadNodes() error {
	sql := `
		WITH RECURSIVE NodeRelationships AS (
			SELECT
				*,
				relationships._class AS relationship_class,
				relationships.metadata AS relationship_metadata
			FROM
				nodes as src
				JOIN relationships ON src.id = relationships.node_from
				WHERE src.id = $1 AND relationships._class = 'COLLECTION_HAS_NODE'
		)
		SELECT
			dst.id,
			dst.name,
			dst._class,
			dst.metadata,
			dst.original_data
		FROM
			NodeRelationships
			JOIN nodes as dst ON dst.id = NodeRelationships.node_to
	`

	rows, err := collection._conn.Query(sql, collection.Id)
	if err != nil {
		return err
	}

	defer rows.Close()

	collection._relationships = make([]StandardRelationship, 0)
	collection.childs = make([]*Node, 0)
	for rows.Next() {
		node := &Node{
			_conn: collection._conn,
		}
		if err := rows.Scan(
			&node.Id,
			&node.name,
			&node._class,
			&node.metadata,
			&node.originalData,
		); err != nil {
			return err
		}

		collection.childs = append(collection.childs, node)
	}

	return nil
}

// NewCollectionObject creates a new Collection instance without persisting it to the database.
// This is useful when you want to prepare a Collection for later storage.
func NewCollection(name string, metadata []byte) *Collection {
	return &Collection{
		Node: Node{
			name:     name,
			_class:   "COLLECTION",
			metadata: metadata,
			Id:       -1, // Use -1 to indicate not persisted
		},
		childs:     make([]*Node, 0),
		is_default: false,
	}
}

// Internal RelationshipClass to handle the collection to node relationship
type collection_has_node struct {
	Relationship
}

func (col_has_node *collection_has_node) GetClass() string {
	return "COLLECTION_HAS"
}

func (col_has_node *collection_has_node) GetMetadata() []byte {
	return nil
}

func (col_has_node *collection_has_node) FromRelationship(_class string, metadata []byte) error {
	if _class != "COLLECTION_HAS" {
		return fmt.Errorf("invalid class %s", _class)
	}
	return nil
}

// Adds a new child to this collection. Use the underlaying node's AddRelation
// method.
func (collection *Collection) AddChild(node *Node) error {
	_, err := collection.StoreRelation(&collection_has_node{}, node.Id)
	if err != nil {
		return err
	}

	collection.childs = append(collection.childs, node)

	return nil
}

func (collection *Collection) IsDefault() bool {
	return collection.is_default
}

// Is a type alias for FetchResponse containing a slice of Collection pointers.
type FetchNodesResponse = FetchResponse[[]*Node]

// Fetches collections using the provided fetcher and pagination settings.
// It updates the platform's collections and creates relationships between the platform and the collections.
//
// Parameters:
// - ctx: The context to control cancellation.
// - fetcher: The fetcher function to execute the work.
// - start_pagination: The initial pagination settings.
// - pool_config: The configuration for the worker pool.
//
// Returns:
// - error: The error if any occurred.
func (collection *Collection) FetchNodes(
	ctx context.Context,
	fetcher Work[Pagination, FetchNodesResponse],
	startPagination Pagination,
	poolConfig *WorkConfig,
) error {
	fmt.Printf("Fetching nodes for Collection: %d - %v\n", collection.Id, collection.name)
	values, err := fetchWithPagination(ctx, poolConfig, fetcher, startPagination)
	if err != nil {
		return err
	}

	collection.childs = slices.Concat(collection.childs, values)

	fmt.Printf("Nodes added: %d, Nodes in collection: %d\n", len(values), len(collection.childs))

	err = BulkCreateNode(collection._conn, values)
	if err != nil {
		return err
	}

	relationships := make([]*Relationship, 0, len(values))

	for _, item := range values {
		relation := &Relationship{
			_class: "COLLECTION_HAS_NODE",
			From:   collection.Id,
			To:     item.Id,
		}

		err := collection.AddRelationship(relation)
		if err != nil {
			return err
		}
		relationships = append(relationships, relation)
	}

	err = BulkCreateRelationships(collection._conn, relationships)
	if err != nil {
		return err
	}

	return nil
}

func PushNodes[T any](
	ctx context.Context,
	collection *Collection,
	fetcher Work[T, string],
	poolConfig *WorkConfig,
) error {
	fmt.Printf("Pushing nodes for Collection: %d - %v\n", collection.Id, collection.name)

	tasks := make(chan T)

	values, errors, doneChannel := asyncTaskRunner[T, string](
		ctx,
		tasks,
		poolConfig,
		fetcher,
	)

	for _, node := range collection.childs {
		var child T
		json.Unmarshal(node.GetMetadata(), &child)
		tasks <- child
	}

	close(tasks)

	for {
		select {
		case <-values:
			// TODO: add external id to node, so we can update it later
			continue
		case error, ok := <-errors:
			if !ok {
				continue
			}
			return error
		case <-ctx.Done():
			return ctx.Err()
		case <-doneChannel:
			return nil
		}
	}
}

type Reconcilation[T any] func(src *T) (*Node, error)

func ReconciliateCollections[T any](src, dst *Collection, work Reconcilation[T]) error {
	newNodes := make([]*Node, 0, len(src.childs))
	updateNodes := make([]*Node, 0, len(src.childs))
	for _, srcNode := range src.childs {
		var metadata T
		err := json.Unmarshal(srcNode.metadata, &metadata)
		if err != nil {
			return err
		}

		dstNode, err := work(&metadata)
		if err != nil {
			return err
		}

		if dstNode == nil {
			return fmt.Errorf("Node pointer is null")
		}

		if dstNode.Id == -1 {
			newNodes = append(newNodes, dstNode)
		} else {
			updateNodes = append(updateNodes, dstNode)
		}
	}

	BulkCreateNode(src._conn, newNodes)
	// BulkUpdateNode(src._conn, updateNodes)

	relationships := make([]*Relationship, 0, len(newNodes)+len(updateNodes))

	appendRelationship := func(item *Node) error {
		relation := &Relationship{
			_class: "COLLECTION_HAS_NODE",
			From:   dst.Id,
			To:     item.Id,
		}

		err := dst.AddRelationship(relation)
		if err != nil {
			return err
		}
		relationships = append(relationships, relation)

		return nil
	}

	for _, item := range newNodes {
		err := appendRelationship(item)
		if err != nil {
			return err
		}
	}

	for _, item := range updateNodes {
		err := appendRelationship(item)
		if err != nil {
			return err
		}
	}

	err := BulkCreateRelationships(dst._conn, relationships)
	if err != nil {
		return err
	}

	return nil
}