/**
 * Template and template argument handling, first cut.
 *
 * AsyncTokenTransformManager objects provide preprocessor-frame-like
 * functionality once template args etc are fully expanded, and isolate
 * individual transforms from concurrency issues. Template expansion is
 * controlled using a tplExpandData structure created independently for each
 * handled template tag.
 *
 * @author Gabriel Wicke <gwicke@wikimedia.org>
 * @author Brion Vibber <brion@wikimedia.org>
 */
var $ = require('jquery'),
	events = require('events'),
	ParserFunctions = require('./ext.core.ParserFunctions.js').ParserFunctions,
	AttributeTransformManager = require('./mediawiki.TokenTransformManager.js')
									.AttributeTransformManager,
	defines = require('./mediawiki.parser.defines.js'),
	TemplateRequest = require('./mediawiki.ApiRequest.js').TemplateRequest;


function TemplateHandler ( manager ) {
	this.register( manager );
	this.parserFunctions = new ParserFunctions( manager );
}

// constants
TemplateHandler.prototype.rank = 1.1;

TemplateHandler.prototype.register = function ( manager ) {
	this.manager = manager;
	// Register for template and templatearg tag tokens
	manager.addTransform( this.onTemplate.bind(this), 
			this.rank, 'tag', 'template' );

	// Template argument expansion
	manager.addTransform( this.onTemplateArg.bind(this), 
			this.rank, 'tag', 'templatearg' );

};


/** 
 * Main template token handler
 *
 * Expands target and arguments (both keys and values) and either directly
 * calls or sets up the callback to _expandTemplate, which then fetches and
 * processes the template.
 */
TemplateHandler.prototype.onTemplate = function ( token, frame, cb ) {
	//console.warn('onTemplate! ' + JSON.stringify( token, null, 2 ) + 
	//		' args: ' + JSON.stringify( this.manager.args ));

	// expand argument keys, with callback set to next processing step
	// XXX: would likely be faster to do this in a tight loop here
	var atm = new AttributeTransformManager( 
				this.manager, 
				this._expandTemplate.bind( this, token, frame, cb )
			);
	cb( { async: true } );
	atm.processKeys( token.attribs );
};

/**
 * Create positional (number) keys for arguments without explicit keys
 */
TemplateHandler.prototype._nameArgs = function ( attribs ) {
	var n = 1,
		out = [];
	for ( var i = 0, l = attribs.length; i < l; i++ ) {
		// FIXME: Also check for whitespace-only named args!
		if ( ! attribs[i].k.length ) {
			out.push( new KV( n.toString(), attribs[i].v ) );
			n++;
		} else {
			out.push( attribs[i] );
		}
	}
	this.manager.env.dp( '_nameArgs: ', out );
	return out;
};

/**
 * Fetch, tokenize and token-transform a template after all arguments and the
 * target were expanded.
 */
TemplateHandler.prototype._expandTemplate = function ( token, frame, cb, attribs ) {
	//console.warn('TemplateHandler.expandTemplate: ' +
	//		JSON.stringify( tplExpandData, null, 2 ) );
	var target = attribs[0].k;

	
	if ( ! target ) {
		this.manager.env.ap( 'No target! ', attribs );
		console.trace();
	}

	// TODO:
	// check for 'subst:'
	// check for variable magic names
	// check for msg, msgnw, raw magics
	// check for parser functions

	// First, check the target for loops
	target = this.manager.env.tokensToString( target ).trim();

	//var args = this.manager.env.KVtoHash( tplExpandData.expandedArgs );

	// strip subst for now.
	target = target.replace( /^(safe)?subst:/, '' );

	// XXX: wrap attribs in object with .dict() and .named() methods,
	// and each member (key/value) into object with .tokens(), .dom() and
	// .wikitext() methods (subclass of Array)

	var prefix = target.split(':', 1)[0].toLowerCase().trim();
	if ( prefix && 'pf_' + prefix in this.parserFunctions ) {
		var pfAttribs = new Params( this.manager.env, attribs );
		pfAttribs[0] = new KV( target.substr( prefix.length + 1 ), [] );
		//this.manager.env.dp( 'func prefix/args: ', prefix,
		//		tplExpandData.expandedArgs,
		//		'unnamedArgs', tplExpandData.origToken.attribs,
		//		'funcArg:', funcArg
		//		);
		this.manager.env.dp( 'entering prefix', target, token  );
		this.parserFunctions[ 'pf_' + prefix ]
			( token, this.manager.frame, cb, pfAttribs );
		return;
	}
	this.manager.env.tp( 'template target: ' + target );

	// now normalize the target before template processing
	target = this.manager.env.normalizeTitle( target );

	

	// Resolve a possibly relative link
	var templateName = this.manager.env.resolveTitle( 
			target,
			'Template' 
		);

	var checkRes = this.manager.frame.loopAndDepthCheck( templateName, this.manager.env.maxDepth );
	if( checkRes ) {
		// Loop detected or depth limit exceeded, abort!
		res = [
				checkRes,
				new TagTk( 'a', [{k: 'href', v: target}] ),
				templateName,
				new EndTagTk( 'a' )
			];
		res.rank = this.manager.phaseEndRank;
		cb( { tokens: res } );
		return;
	}

	// XXX: notes from brion's mediawiki.parser.environment
	// resolve template name
	// load template w/ canonical name
	// load template w/ variant names (language variants)

	// For now, just fetch the template and pass the callback for further
	// processing along.
	this._fetchTemplateAndTitle( 
			templateName, 
			cb,
			this._processTemplateAndTitle.bind( this, token, frame, cb, templateName, attribs )
		);
};


/**
 * Process a fetched template source
 */
TemplateHandler.prototype._processTemplateAndTitle = function( token, frame, cb, name, attribs, src, type ) {
	// Get a nested transformation pipeline for the input type. The input
	// pipeline includes the tokenizer, synchronous stage-1 transforms for
	// 'text/wiki' input and asynchronous stage-2 transforms). 
	var pipeline = this.manager.pipeFactory.getPipeline( 
				type || 'text/x-mediawiki', true
			);

	pipeline.setFrame( this.manager.frame, name, attribs );

	// Hook up the inputPipeline output events to our handlers
	pipeline.addListener( 'chunk', this._onChunk.bind ( this, cb ) );
	pipeline.addListener( 'end', this._onEnd.bind ( this, cb ) );
	// Feed the pipeline. XXX: Support different formats.
	this.manager.env.dp( 'TemplateHandler._processTemplateAndTitle', name, attribs );
	pipeline.process ( src, name );
};

/**
 * Handle chunk emitted from the input pipeline after feeding it a template
 */
TemplateHandler.prototype._onChunk = function( cb, chunk ) {
	// We encapsulate the output by default, so collect tokens here.
	chunk = this.manager.env.stripEOFTkfromTokens( chunk );
	this.manager.env.dp( 'TemplateHandler._onChunk', chunk );
	cb( { tokens: chunk, async: true } );
};

/**
 * Handle the end event emitted by the parser pipeline after fully processing
 * the template source.
 */
TemplateHandler.prototype._onEnd = function( cb ) {
	this.manager.env.dp( 'TemplateHandler._onEnd' );
	cb( { tokens: [] } );
};


/**
 * Fetch a template
 */
TemplateHandler.prototype._fetchTemplateAndTitle = function ( title, parentCB, cb ) {
	// @fixme normalize name?
	var self = this;
	if ( title in this.manager.env.pageCache ) {
		// XXX: store type too (and cache tokens/x-mediawiki)
		cb( self.manager.env.pageCache[title] /* , type */ );
	} else if ( ! this.manager.env.fetchTemplates ) {
		parentCB(  { tokens: [ 'Warning: Page/template fetching disabled, and no cache for ' + 
				title ] } );
	} else {
		
		// We are about to start an async request for a template
		this.manager.env.dp( 'Note: trying to fetch ', title );

		// Start a new request if none is outstanding
		//this.manager.env.dp( 'requestQueue: ', this.manager.env.requestQueue );
		if ( this.manager.env.requestQueue[title] === undefined ) {
			this.manager.env.tp( 'Note: Starting new request for ' + title );
			this.manager.env.requestQueue[title] = new TemplateRequest( this.manager.env, title );
		}
		// Append a listener to the request at the toplevel, but prepend at
		// lower levels to enforce depth-first processing
		if ( false && this.manager.isInclude ) {
			// prepend request: deal with requests from includes first
			this.manager.env.requestQueue[title]
				.listeners( 'src' ).unshift( cb );
		} else {
			// append request, process in document order
			this.manager.env.requestQueue[title]
				.listeners( 'src' ).push( cb );
		}
		parentCB ( { async: true } );
	}
};


/*********************** Template argument expansion *******************/

/**
 * Expand template arguments with tokens from the containing frame.
 */
TemplateHandler.prototype.onTemplateArg = function ( token, frame, cb ) {
	new AttributeTransformManager ( 
				this.manager, 
				this._returnArgAttributes.bind( this, token, cb, frame ) 
			).process( token.attribs.slice() );
};

TemplateHandler.prototype._returnArgAttributes = function ( token, cb, frame, attributes ) {
	//console.warn( '_returnArgAttributes: ' + JSON.stringify( attributes ));
	var argName = this.manager.env.tokensToString( attributes[0].k ).trim(),
		res,
		dict = this.manager.frame.args.named();
	this.manager.env.dp( 'args', argName /*, dict*/ );
	if ( argName in dict ) {
		// return tokens for argument
		//console.warn( 'templateArg found: ' + argName + 
		//		' vs. ' + JSON.stringify( this.manager.args ) ); 
		res = dict[argName];
		this.manager.env.dp( 'arg res:', res );
		if ( res.constructor === String ) {
			cb( { tokens: [res] } );
		} else {
			dict[argName].get({
				type: 'tokens/x-mediawiki/expanded',
				cb: function( res ) { cb ( { tokens: res } ); },
				asyncCB: cb
			});
		}
		return;
	} else {
		this.manager.env.dp( 'templateArg not found: ', argName
				/*' vs. ', dict */ );
		if ( attributes.length > 1 ) {
			res = attributes[1].v;
		} else {
			//console.warn('no default for ' + argName + JSON.stringify( attributes ));
			res = [ '{{{' + argName + '}}}' ];
		}
	}
	cb( { tokens: res } );
};





if (typeof module == "object") {
	module.exports.TemplateHandler = TemplateHandler;
}