/*\
title: $:/plugins/tiddlywiki/multiwikiserver/sql-tiddler-database.js
type: application/javascript
module-type: library

Low level SQL functions to store and retrieve tiddlers in a SQLite database.

This class is intended to encapsulate all the SQL queries used to access the database.
Validation is for the most part left to the caller

\*/

(function() {

/*
Create a tiddler store. Options include:

databasePath - path to the database file (can be ":memory:" to get a temporary database)
engine - wasm | better
*/
function SqlTiddlerDatabase(options) {
	options = options || {};
	// Initialise the statement cache
	this.statements = Object.create(null); // Hashmap by SQL text of statement objects
	// Create the database file directories if needed
	if(options.databasePath) {
		$tw.utils.createFileDirectories(options.databasePath);
	}
	// Choose engine
	this.engine = options.engine || "better"; // wasm | better
	// Create the database
	const databasePath = options.databasePath || ":memory:";
	let Database;
	console.log(`Creating SQL engine ${this.engine}`)
	switch(this.engine) {
		case "wasm":
			({ Database } = require("node-sqlite3-wasm"));
			break;
		case "better":
			Database = require("better-sqlite3");
			break;
	}
	this.db = new Database(databasePath,{
		verbose: undefined && console.log
	});
	this.transactionDepth = 0;
}

SqlTiddlerDatabase.prototype.close = function() {
	for(const sql in this.statements) {
		if(this.statements[sql].finalize) {
			this.statements[sql].finalize();
		}
	}
	this.statements = Object.create(null);
	this.db.close();
	this.db = undefined;
};

SqlTiddlerDatabase.prototype.normaliseParams = function(params) {
	params = params || {};
	const result = Object.create(null);
	for(const paramName in params) {
		if(this.engine !== "wasm" && paramName.startsWith("$")) {
			result[paramName.slice(1)] = params[paramName];
		} else {
			result[paramName] = params[paramName];
		}
	}
	return result;
};

SqlTiddlerDatabase.prototype.prepareStatement = function(sql) {
	if(!(sql in this.statements)) {
		this.statements[sql] = this.db.prepare(sql);
	}
	return this.statements[sql];
};

SqlTiddlerDatabase.prototype.runStatement = function(sql,params) {
	params = this.normaliseParams(params);
	const statement = this.prepareStatement(sql);
	return statement.run(params);
};

SqlTiddlerDatabase.prototype.runStatementGet = function(sql,params) {
	params = this.normaliseParams(params);
	const statement = this.prepareStatement(sql);
	return statement.get(params);
};

SqlTiddlerDatabase.prototype.runStatementGetAll = function(sql,params) {
	params = this.normaliseParams(params);
	const statement = this.prepareStatement(sql);
	return statement.all(params);
};

SqlTiddlerDatabase.prototype.runStatements = function(sqlArray) {
	for(const sql of sqlArray) {
		this.runStatement(sql);
	}
};

SqlTiddlerDatabase.prototype.createTables = function() {
	this.runStatements([`
		-- Bags have names and access control settings
		CREATE TABLE IF NOT EXISTS bags (
			bag_id INTEGER PRIMARY KEY AUTOINCREMENT,
			bag_name TEXT UNIQUE NOT NULL,
			accesscontrol TEXT NOT NULL,
			description TEXT NOT NULL
		)
	`,`
		-- Recipes have names...
		CREATE TABLE IF NOT EXISTS recipes (
			recipe_id INTEGER PRIMARY KEY AUTOINCREMENT,
			recipe_name TEXT UNIQUE NOT NULL,
			description TEXT NOT NULL
		)
	`,`
		-- ...and recipes also have an ordered list of bags
		CREATE TABLE IF NOT EXISTS recipe_bags (
			recipe_id INTEGER NOT NULL,
			bag_id INTEGER NOT NULL,
			position INTEGER NOT NULL,
			FOREIGN KEY (recipe_id) REFERENCES recipes(recipe_id) ON UPDATE CASCADE ON DELETE CASCADE,
			FOREIGN KEY (bag_id) REFERENCES bags(bag_id) ON UPDATE CASCADE ON DELETE CASCADE,
			UNIQUE (recipe_id, bag_id)
		)
	`,`
		-- Tiddlers are contained in bags and have titles
		CREATE TABLE IF NOT EXISTS tiddlers (
			tiddler_id INTEGER PRIMARY KEY AUTOINCREMENT,
			bag_id INTEGER NOT NULL,
			title TEXT NOT NULL,
			FOREIGN KEY (bag_id) REFERENCES bags(bag_id) ON UPDATE CASCADE ON DELETE CASCADE,
			UNIQUE (bag_id, title)
		)
	`,`
		-- Tiddlers also have unordered lists of fields, each of which has a name and associated value
		CREATE TABLE IF NOT EXISTS fields (
			tiddler_id INTEGER,
			field_name TEXT NOT NULL,
			field_value TEXT NOT NULL,
			FOREIGN KEY (tiddler_id) REFERENCES tiddlers(tiddler_id) ON UPDATE CASCADE ON DELETE CASCADE,
			UNIQUE (tiddler_id, field_name)
		)
	`]);
};

SqlTiddlerDatabase.prototype.logTables = function() {
	var self = this;
	function sqlLogTable(table) {
		console.log(`TABLE ${table}:`);
		let statement = self.db.prepare(`select * from ${table}`);
		for(const row of statement.all()) {
			console.log(row);
		}
	}
	const tables = ["recipes","bags","recipe_bags","tiddlers","fields"];
	for(const table of tables) {
		sqlLogTable(table);
	}
};

SqlTiddlerDatabase.prototype.listBags = function() {
	const rows = this.runStatementGetAll(`
		SELECT bag_name, accesscontrol, description
		FROM bags
		ORDER BY bag_name
	`);
	return rows;
};

SqlTiddlerDatabase.prototype.createBag = function(bagname,description,accesscontrol) {
	accesscontrol = accesscontrol || "";
	// Run the queries
	this.runStatement(`
		INSERT OR IGNORE INTO bags (bag_name, accesscontrol, description)
		VALUES ($bag_name, '', '')
	`,{
		$bag_name: bagname
	});
	this.runStatement(`
		UPDATE bags
		SET accesscontrol = $accesscontrol,
		description = $description 
		WHERE bag_name = $bag_name
	`,{
		$bag_name: bagname,
		$accesscontrol: accesscontrol,
		$description: description
	});
};

/*
Returns array of {recipe_name:,description:,bag_names: []}
*/
SqlTiddlerDatabase.prototype.listRecipes = function() {
	const rows = this.runStatementGetAll(`
		SELECT r.recipe_name, r.description, b.bag_name, rb.position
		FROM recipes AS r
		JOIN recipe_bags AS rb ON rb.recipe_id = r.recipe_id
		JOIN bags AS b ON rb.bag_id = b.bag_id
		ORDER BY r.recipe_name, rb.position
	`);
	const results = [];
	let currentRecipeName = null, currentRecipeIndex = -1;
	for(const row of rows) {
		if(row.recipe_name !== currentRecipeName) {
			currentRecipeName = row.recipe_name;
			currentRecipeIndex += 1;
			results.push({
				recipe_name: row.recipe_name,
				description: row.description,
				bag_names: []
			});
		}
		results[currentRecipeIndex].bag_names.push(row.bag_name);
	}
	return results;
};

SqlTiddlerDatabase.prototype.createRecipe = function(recipename,bagnames,description) {
	// Run the queries
	this.runStatement(`
		-- Delete existing recipe_bags entries for this recipe
		DELETE FROM recipe_bags WHERE recipe_id = (SELECT recipe_id FROM recipes WHERE recipe_name = $recipe_name)
	`,{
		$recipe_name: recipename
	});
	this.runStatement(`
		-- Create the entry in the recipes table if required
		INSERT OR REPLACE INTO recipes (recipe_name, description)
		VALUES ($recipe_name, $description)
	`,{
		$recipe_name: recipename,
		$description: description
	});
	this.runStatement(`
		INSERT INTO recipe_bags (recipe_id, bag_id, position)
		SELECT r.recipe_id, b.bag_id, j.key as position
		FROM recipes r
		JOIN bags b
		INNER JOIN json_each($bag_names) AS j ON j.value = b.bag_name
		WHERE r.recipe_name = $recipe_name
	`,{
		$recipe_name: recipename,
		$bag_names: JSON.stringify(bagnames)
	});
};

/*
Returns {tiddler_id:}
*/
SqlTiddlerDatabase.prototype.saveBagTiddler = function(tiddlerFields,bagname) {
	// Update the tiddlers table
	var info = this.runStatement(`
		INSERT OR REPLACE INTO tiddlers (bag_id, title)
		VALUES (
			(SELECT bag_id FROM bags WHERE bag_name = $bag_name),
			$title
		)
	`,{
		$title: tiddlerFields.title,
		$bag_name: bagname
	});
	// Update the fields table
	this.runStatement(`
		INSERT OR REPLACE INTO fields (tiddler_id, field_name, field_value)
		SELECT
			t.tiddler_id,
			json_each.key AS field_name,
			json_each.value AS field_value
		FROM (
			SELECT tiddler_id
			FROM tiddlers
			WHERE bag_id = (
				SELECT bag_id
				FROM bags
				WHERE bag_name = $bag_name
			) AND title = $title
		) AS t
		JOIN json_each($field_values) AS json_each
	`,{
		$title: tiddlerFields.title,
		$bag_name: bagname,
		$field_values: JSON.stringify(Object.assign({},tiddlerFields,{title: undefined}))
	});
	return {
		tiddler_id: info.lastInsertRowid
	}
};

/*
Returns {tiddler_id:,bag_name:} or null if the recipe is empty
*/
SqlTiddlerDatabase.prototype.saveRecipeTiddler = function(tiddlerFields,recipename) {
	// Find the topmost bag in the recipe
	var row = this.runStatementGet(`
		SELECT b.bag_name
		FROM bags AS b
		JOIN (
			SELECT rb.bag_id
			FROM recipe_bags AS rb
			WHERE rb.recipe_id = (
				SELECT recipe_id
				FROM recipes
				WHERE recipe_name = $recipe_name
			)
			ORDER BY rb.position DESC
			LIMIT 1
		) AS selected_bag
		ON b.bag_id = selected_bag.bag_id
	`,{
		$recipe_name: recipename
	});
	if(!row) {
		return null;
	}
	// Save the tiddler to the topmost bag
	var info = this.saveBagTiddler(tiddlerFields,row.bag_name);
	return {
		tiddler_id: info.tiddler_id,
		bag_name: row.bag_name
	};
};

SqlTiddlerDatabase.prototype.deleteTiddler = function(title,bagname) {
	// Run the queries
	this.runStatement(`
		DELETE FROM fields
		WHERE tiddler_id IN (
			SELECT t.tiddler_id
			FROM tiddlers AS t
			INNER JOIN bags AS b ON t.bag_id = b.bag_id
			WHERE b.bag_name = $bag_name AND t.title = $title
		)
	`,{
		$title: title,
		$bag_name: bagname
	});
	this.runStatement(`
		DELETE FROM tiddlers
		WHERE bag_id = (
			SELECT bag_id
			FROM bags
			WHERE bag_name = $bag_name
		) AND title = $title
	`,{
		$title: title,
		$bag_name: bagname
	});
};

/*
returns {tiddler_id:,tiddler:}
*/
SqlTiddlerDatabase.prototype.getBagTiddler = function(title,bagname) {
	const rows = this.runStatementGetAll(`
		SELECT field_name, field_value, tiddler_id
		FROM fields
		WHERE tiddler_id = (
			SELECT t.tiddler_id
			FROM bags AS b
			INNER JOIN tiddlers AS t ON b.bag_id = t.bag_id
			WHERE t.title = $title AND b.bag_name = $bag_name
		)
	`,{
		$title: title,
		$bag_name: bagname
	});
	if(rows.length === 0) {
		return null;
	} else {
		return {
			tiddler_id: rows[0].tiddler_id,
			tiddler: rows.reduce((accumulator,value) => {
					accumulator[value["field_name"]] = value.field_value;
					return accumulator;
				},{title: title})
		};
	}
};

/*
Returns {bag_name:, tiddler: {fields}, tiddler_id:}
*/
SqlTiddlerDatabase.prototype.getRecipeTiddler = function(title,recipename) {
	const rowTiddlerId = this.runStatementGet(`	
		SELECT t.tiddler_id, b.bag_name
		FROM bags AS b
		INNER JOIN recipe_bags AS rb ON b.bag_id = rb.bag_id
		INNER JOIN recipes AS r ON rb.recipe_id = r.recipe_id
		INNER JOIN tiddlers AS t ON b.bag_id = t.bag_id
		WHERE r.recipe_name = $recipe_name
		AND t.title = $title
		ORDER BY rb.position DESC
		LIMIT 1
	`,{
		$title: title,
		$recipe_name: recipename
	});
	if(!rowTiddlerId) {
		return null;
	}
	// Get the fields
	const rows = this.runStatementGetAll(`
		SELECT field_name, field_value
		FROM fields
		WHERE tiddler_id = $tiddler_id
	`,{
		$tiddler_id: rowTiddlerId.tiddler_id
	});
	return {
		bag_name: rowTiddlerId.bag_name,
		tiddler_id: rowTiddlerId.tiddler_id,
		tiddler: rows.reduce((accumulator,value) => {
				accumulator[value["field_name"]] = value.field_value;
				return accumulator;
			},{title: title})
	};
};

/*
Get the titles of the tiddlers in a bag. Returns an empty array for bags that do not exist
*/
SqlTiddlerDatabase.prototype.getBagTiddlers = function(bagname) {
	const rows = this.runStatementGetAll(`
		SELECT DISTINCT title
		FROM tiddlers
		WHERE bag_id IN (
			SELECT bag_id
			FROM bags
			WHERE bag_name = $bag_name
		)
		ORDER BY title ASC
	`,{
		$bag_name: bagname
	});
	return rows.map(value => value.title);
};

/*
Get the titles of the tiddlers in a recipe as {title:,bag_name:}. Returns an empty array for recipes that do not exist
*/
SqlTiddlerDatabase.prototype.getRecipeTiddlers = function(recipename) {
	const rows = this.runStatementGetAll(`
		SELECT title, bag_name
		FROM (
			SELECT t.title, b.bag_name, MAX(rb.position) AS position
			FROM bags AS b
			INNER JOIN recipe_bags AS rb ON b.bag_id = rb.bag_id
			INNER JOIN recipes AS r ON rb.recipe_id = r.recipe_id
			INNER JOIN tiddlers AS t ON b.bag_id = t.bag_id
			WHERE r.recipe_name = $recipe_name
			GROUP BY t.title
			ORDER BY t.title
		)
	`,{
		$recipe_name: recipename
	});
	return rows;
};

SqlTiddlerDatabase.prototype.deleteAllTiddlersInBag = function(bagname) {
	this.runStatement(`
		DELETE FROM tiddlers
		WHERE bag_id IN (
			SELECT bag_id
			FROM bags
			WHERE bag_name = $bag_name
		)
	`,{
		$bag_name: bagname
	});
};

/*
Get the names of the bags in a recipe. Returns an empty array for recipes that do not exist
*/
SqlTiddlerDatabase.prototype.getRecipeBags = function(recipename) {
	const rows = this.runStatementGetAll(`
		SELECT bags.bag_name
		FROM bags
		JOIN (
			SELECT rb.bag_id, rb.position as position
			FROM recipe_bags AS rb
			JOIN recipes AS r ON rb.recipe_id = r.recipe_id
			WHERE r.recipe_name = $recipe_name
			ORDER BY rb.position
		) AS bag_priority ON bags.bag_id = bag_priority.bag_id
		ORDER BY position
	`,{
		$recipe_name: recipename
	});
	return rows.map(value => value.bag_name);
};

/*
Execute the given function in a transaction, committing if successful but rolling back if an error occurs.  Returns whatever the given function returns.

Calls to this function can be safely nested, but only the topmost call will actually take place in a transaction.

TODO: better-sqlite3 provides its own transaction method which we should be using if available
*/
SqlTiddlerDatabase.prototype.transaction = function(fn) {
	const alreadyInTransaction = this.transactionDepth > 0;
	this.transactionDepth++;
	if(alreadyInTransaction) {
		return fn();
	} else {
		this.runStatement(`BEGIN TRANSACTION`);
		try {
			var result = fn();
			this.runStatement(`COMMIT TRANSACTION`);
		} catch(e) {
			this.runStatement(`ROLLBACK TRANSACTION`);
			throw(e);
		} finally {
			this.transactionDepth--;
		}
		return result;
	}
};

exports.SqlTiddlerDatabase = SqlTiddlerDatabase;

})();