// Package synchronizator: Provides a library to help synchronize data from
// different sources.
//
// It does so implementing a graph database representing the relation of the
// different entities of data called "nodes", helping you find, create or
// delete the "equivalent" entities in the different sources.
//
// In this library we use the following nomemclature:
// - [struct_name]: The representation of the element in the database
// - [struct_name]Class: An interface so the users can create a custom representation of the element that make's sence in their application. The interface needs to provide a way to transform the struct into a node and viceversa.
package synchronizator

import (
	sql "database/sql"
	"encoding/json"
	"fmt"
	"os"
	"time"
)

// DB Syncronization database interface
type DB struct {
	Connection  *sql.DB // underliying database connection
	logger      *os.File
	log_level   LogLevel
	drop_tables bool
}

// Options for the DB struct
type Options struct {
	Logger                  *os.File // Where to log, defaults to os.Stdout
	Log_level               LogLevel // Log level, defaults to INFO
	DANGEROUSLY_DROP_TABLES bool     // Drop tables on initialization, defaults to false
}

type LogLevel int

// The log levels, lower levels take precedence
//
//go:generate stringer -type=LogLevel
const (
	ERROR LogLevel = iota
	INFO
	DEBUG
)

var DefaultOptions = &Options{
	Logger:                  os.Stdout,
	Log_level:               INFO,
	DANGEROUSLY_DROP_TABLES: false,
}

// Constructor for the DB struct, it's dicourage to create the struct yourself!
// It receives a pointer to a sql.DB connection and an optional pointer to an Options struct.
//
// You need to initialize the connection yourself, this library does not handle that and only use the provided connection.
// This also alows to append this labrary tables to your already existing database.
func New(connection *sql.DB, options *Options) (*DB, error) {
	if options == nil {
		options = DefaultOptions
	}

	conn := DB{
		Connection:  connection,
		logger:      options.Logger,
		log_level:   options.Log_level,
		drop_tables: options.DANGEROUSLY_DROP_TABLES,
	}

	err := conn.bootstrap()
	if err != nil {
		return nil, err
	}

	return &conn, nil
}

// Write a log message to the logger.
//
// It receives a LogLevel and a variadic argument that is directly passed to fmt.Fprintln.
// The log is only written if the LogLevel is the same or lower than the configured value in the struct.
func (conn *DB) log(level LogLevel, args ...any) {
	if level > conn.log_level {
		return
	}

	fmt.Fprintf(conn.logger, "[ %s - %-5s ]: ", time.Now().Format(time.DateTime), level.String())
	fmt.Fprintln(conn.logger, args...)
}

// Initialize the database, creating the tables and indexes.
func (conn *DB) bootstrap() error {
	conn.log(INFO, "Initializing database...")

	sql := ""

	if conn.drop_tables {
		sql += `
			DROP TABLE IF EXISTS nodes;
			DROP TABLE IF EXISTS relationships;
			DROP INDEX IF EXISTS node_class;
			DROP INDEX IF EXISTS relationships_class;
		`
	}

	sql += `
    CREATE TABLE IF NOT EXISTS nodes (
      id INTEGER PRIMARY KEY AUTOINCREMENT,
      _class text NOT NULL,
			name TEXT,
      metadata jsonb DEFAULT '{}'
    );

    CREATE INDEX IF NOT EXISTS node_class on nodes (_class);


    CREATE TABLE IF NOT EXISTS relationships (
      node_from INTEGER NOT NULL,
      node_to INTEGER NOT NULL,
      _class text NOT NULL,
      metadata jsonb DEFAULT '{}',
      PRIMARY KEY (node_from, node_to),
      CHECK (node_from != node_to),
      CONSTRAINT fk_node_from_relationships FOREIGN KEY (node_from) REFERENCES nodes(id),
      CONSTRAINT fk_node_to_relationships FOREIGN KEY (node_to) REFERENCES nodes(id)
    );

    CREATE INDEX IF NOT EXISTS relationships_class on relationships (_class);
  `

	conn.log(DEBUG, sql)
	_, err := conn.Connection.Exec(sql)
	if err != nil {
		return err
	}

	return nil
}

// Allows you to run the underliying query in a transaction.
func (conn *DB) withTx(fn func(*sql.Tx) error) error {
	tx, err := conn.Connection.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()

	if err := fn(tx); err != nil {
		return err
	}

	return tx.Commit()
}

func (conn *DB) Query(sql string, args ...any) (*sql.Rows, error) {
	conn.log(DEBUG, "Executing query:", sql, args)

	rows, err := conn.Connection.Query(sql, args...)
	if err != nil {
		return nil, err
	}

	return rows, nil
}

// Creates a new Platform with the provided data.
//
// A collection is only a Node wrapper with some extended functionality to
// manage multiple nodes. For more information see [DB.NewNode] method and the
// [Platform] struct.
func (conn *DB) NewPlatform(data StandardNode) (*Platform, error) {
	var platform *Platform
	err := conn.withTx(func(tx *sql.Tx) error {
		node, err := conn.newNodewithTx(tx, "PLATFORM", data)
		if err != nil {
			return err
		}

		collection, err := conn.newCollectionwithTx(
			tx,
			&default_collection{platform_name: node.name},
		)
		if err != nil {
			return err
		}

		platform := &Platform{
			Node:        *node,
			collections: []*Collection{collection},
		}

		_, err = conn.addRelationwithTx(tx, platform.Id, &collection_relation{}, collection.Id)
		if err != nil {
			return err
		}

		return nil
	})
	return platform, err
}

// Creates a new Collection with the provided data.
//
// A collection is only a Node wrapper with some extended functionality to
// manage multiple nodes. For more information see [DB.NewNode] method and the
// [Collection] struct.
//
// The operation is ran in a database transaction.
func (conn *DB) NewCollection(data StandardNode) (*Collection, error) {
	var collection *Collection

	err := conn.withTx(func(tx *sql.Tx) error {
		var err error
		collection, err = conn.newCollectionwithTx(tx, data)
		return err
	})

	return collection, err
}

// Creates a new Collection with the provided data.
//
// A collection is only a Node wrapper with some extended functionality to
// manage multiple nodes. For more information see [DB.NewNode] method and the
// [Collection] struct.
func (conn *DB) newCollectionwithTx(tx *sql.Tx, data StandardNode) (*Collection, error) {
	node, err := conn.newNodewithTx(tx, "COLLECTION", data)
	if err != nil {
		return nil, err
	}

	collection := &Collection{
		Node:   *node,
		childs: make([]*Node, 0),
	}

	return collection, err
}

// Creates a new node.
//
// The operation is ran in a database transaction.
func (conn *DB) NewNode(class string, data StandardNode) (*Node, error) {
	var node *Node

	err := conn.withTx(func(tx *sql.Tx) error {
		var err error
		node, err = conn.newNodewithTx(tx, class, data)
		return err
	})

	return node, err
}

// Creates a new node
func (conn *DB) newNodewithTx(tx *sql.Tx, class string, data StandardNode) (*Node, error) {
	name, metadata, err := data.ToNode()
	if err != nil {
		return nil, err
	}

	node := Node{
		_conn:    conn,
		_class:   class,
		name:     name,
		metadata: metadata,
		Id:       -1,
	}

	conn.log(DEBUG, "Creating node:", node)

	sql := "INSERT INTO nodes (_class, name, metadata) VALUES ($1, $2, $3) RETURNING id;"

	err = tx.QueryRow(sql, node._class, node.name, metadata).Scan(&node.Id)
	if err != nil {
		return nil, err
	}

	return &node, nil
}

// Updates a node with the provided id and data
func (conn *DB) UpdateNode(id int64, data StandardNode) (*Node, error) {
	name, metadata, err := data.ToNode()
	if err != nil {
		return nil, err
	}

	node := Node{
		_conn:    conn,
		name:     name,
		metadata: metadata,
		Id:       id,
	}

	tx, err := conn.Connection.Begin()
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()
	conn.log(DEBUG, "Updating node:", id, node)

	sql := "UPDATE nodes SET _class = $1, name = $2, metadata = $3 WHERE id = $4;"

	_, err = tx.Exec(sql, node._class, node.name, node.metadata, id)
	if err != nil {
		return nil, err
	}

	if err := tx.Commit(); err != nil {
		return nil, err
	}

	return &node, nil
}

// Return a node with the provided id
func (conn *DB) GetNode(id int64) (*Node, error) {
	node := Node{
		Id:    id,
		_conn: conn,
	}
	sql := "SELECT _class, name, metadata FROM nodes WHERE id = $1;"
	conn.log(DEBUG, sql)

	err := conn.Connection.QueryRow(sql, id).Scan(&node._class, &node.name, &node.metadata)
	if err != nil {
		conn.log(DEBUG, err)
		return nil, fmt.Errorf("No row matching id = %v", id)
	}

	return &node, nil
}

// Deletes a node with the provided id
func (conn *DB) DeleteNode(id int64) error {
	tx, err := conn.Connection.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()

	conn.log(DEBUG, "Deleting node:", id)
	sql := "DELETE FROM nodes WHERE id = $1;"

	_, err = tx.Exec(sql, id)
	if err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return err
	}
	return nil
}

// Creates a new node.
//
// The operation is ran in a database transaction.
func (conn *DB) AddRelation(
	from int64,
	data StandardRelationship,
	to int64,
) (*Relationship, error) {
	var relationship *Relationship

	err := conn.withTx(func(tx *sql.Tx) error {
		var err error
		relationship, err = conn.addRelationwithTx(tx, from, data, to)
		return err
	})

	return relationship, err
}

// Creates a new relationship between two nodes.
//
// It returns the created relationship representation.
func (conn *DB) addRelationwithTx(
	tx *sql.Tx,
	from int64,
	data StandardRelationship,
	to int64,
) (*Relationship, error) {
	class, metadata, err := data.ToRelationship()
	if err != nil {
		return nil, err
	}

	relationship := Relationship{
		_conn:    conn,
		_class:   class,
		Metadata: metadata,
		From:     from,
		To:       to,
	}

	conn.log(DEBUG, "Creating relationship:", from, relationship, to)

	sql := "INSERT INTO relationships (_class, node_from, node_to, metadata) VALUES ($1, $2, $3, $4) RETURNING node_from, node_to;"

	_, err = tx.Exec(sql, relationship._class, relationship.From, relationship.To, metadata)
	if err != nil {
		return nil, err
	}

	return &relationship, nil
}

// Updates a relationship for the provided id and data
func (conn *DB) UpdateRelation(from int64, metadata any, to int64) error {
	if metadata == nil {
		return fmt.Errorf("metadata cannot be nil")
	}
	json_metadata, err := json.Marshal(metadata)
	if err != nil {
		return fmt.Errorf("invalid metadata format: %w", err)
	}
	tx, err := conn.Connection.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()
	conn.log(DEBUG, "Updating relationship:", from, metadata, to)
	sql := "UPDATE relationships SET metadata = $1 WHERE node_from = $2 AND node_to = $3;"
	_, err = tx.Exec(sql, json_metadata, from, to)
	if err != nil {
		return err
	}
	if err := tx.Commit(); err != nil {
		return err
	}
	return nil
}

// Deletes a relationship for the provided id
func (conn *DB) DeleteRelation(from int64, to int64) error {
	tx, err := conn.Connection.Begin()
	if err != nil {
		return err
	}

	defer tx.Rollback()

	sql := "DELETE FROM relationships WHERE node_from = $1 AND node_to = $2;"
	conn.log(DEBUG, "Deleting relationship:", from, to)
	_, err = tx.Exec(sql, from, to)
	if err != nil {
		return nil
	}

	if err := tx.Commit(); err != nil {
		return err
	}

	return nil
}