'use strict';

var events  = require('events');
var fetch   = require('fetch');
var fs      = require('fs-extra');
var factory = require('./factory');
var config  = require('./asset-assembler-config');


function buildEnd(builder, targetFile, resultUriList, callback) {
	fs.appendFile(targetFile, builder.config.assetFooter, function (err) {
		if (err) {
			callback(err);
		} else {
			var buildTime = new Date().getTime() - builder.startTime,
				buildResultSize = resultUriList.length,
				targetStats = fs.statSync(targetFile),
				targetSize = targetStats.size;
			
			if (builder.config.linkTargetSingleResult) {
				resultUriList = [builder.config.linkTarget];
			}
			builder.emit('file-write-post',targetFile);
			builder.emit('log','debug','target size: '+targetSize);
			builder.emit('log','info','build result size: '+resultUriList.length+' from: '+buildResultSize);
			builder.emit('log','info','build done in: '+buildTime+' ms.');
			builder.emit('result',resultUriList);
			builder.emit('end');
			callback();
		}
	});
}


function downloadFile(builder, remoteUrl, localFile, callback) {
	builder.emit('file-download-pre',remoteUrl);
	builder.emit('log','debug','downloadFile: '+remoteUrl);
	fs.ensureFile(localFile, function(err) {
		if (err) {
			callback(err);
		} else {
			var stream = new fetch.FetchStream(remoteUrl);
			stream.on('error', function(err) {
				callback(err);
			});
			stream.on('end', function() {
				builder.emit('file-download-post',remoteUrl);
				callback();
			});
			stream.pipe(fs.createWriteStream(localFile));
		}
	});
}


function downloadFileList(builder, downloadList, callback) {
	if (downloadList.length === 0) {
		callback();
		return;
	}
	var download = downloadList.pop();
	downloadFile(builder, download.remoteUrl, download.localFile, function(err) {
		if (err) {
			callback(err);
		} else {
			downloadFileList(builder, downloadList, callback);
		}
	});
}

function aggregateFileList(builder, targetFile, aggregateList, readFile, callback) {
	if (aggregateList.length === 0) {
		callback();
		return;
	}
	var aggregateFile = aggregateList.pop();
	builder.emit('file-read-pre',aggregateFile);
	readFile(aggregateFile, function(err, data) {
		if (err) {
			callback(err);
		} else {
			builder.emit('file-read-post',aggregateFile);
			builder.emit('log','debug','readFile: '+aggregateFile+' size: '+data.length);
			if (aggregateList.length > 0) {
				data = data + builder.config.assetSeperator;
			}
			fs.appendFile(targetFile, data, function (err) {
				if (err) {
					callback(err);
				} else {
					aggregateFileList(builder, targetFile, aggregateList, readFile, callback);
				}
			});
		}
	});
}

function mapLocalFileSync(assembler, linkSource) {
	var uriMapping = assembler.config.linkMapping;
	if (uriMapping) {
		var uriMappingKeys = Object.keys(uriMapping);
		uriMappingKeys.sort(function(a, b) {
			return a.length < b.length; // longest first as we break on first hit
		});
		for (var ii = 0; ii < uriMappingKeys.length; ii++) {
			var uriKey = uriMappingKeys[ii];
			var localPath = uriMapping[uriKey];
			var mapIndex = linkSource.indexOf(uriKey);
			if (mapIndex === 0) {
				return localPath+linkSource.substring(uriKey.length);
			}
		}
	}
	return linkSource;
}

function buildAsset(builder, targetFile, readFile, callback) {
	var uriList = builder.config.linkSources;
	var localFileList = [];
	var resultUriList = [];
	var downloadList = [];
	
	for (var i = 0; i < uriList.length; i++) {
		var assetItem = uriList[i];
		
		var remoteUrl = null;
		var remoteForce = null;
		var remoteIndex = assetItem.indexOf('@');
		if (remoteIndex > 0) {
			remoteUrl = assetItem.substring(remoteIndex + 1);
			if (remoteUrl.indexOf('@') === 0) {
				remoteUrl = assetItem.substring(remoteIndex + 2);
				remoteForce = true;
			}
			assetItem = assetItem.substring(0,remoteIndex);
		}
		var localFile = mapLocalFileSync(builder, assetItem);
		
		// override force on all files
		if (remoteForce===undefined && builder.config.downloadForce !== undefined) {
			remoteForce = builder.config.downloadForce;
		}
		
		if (remoteUrl && (remoteForce || !fs.existsSync(localFile))) {
			downloadList.push({
				remoteUrl: remoteUrl,
				localFile: localFile
			});
		}
		localFileList.push(localFile);
		resultUriList.push(assetItem);
	}
	downloadList.reverse();
	localFileList.reverse();
	
	downloadFileList(builder, downloadList, function(err) {
		if (err) {
			callback(err);
		} else {
			//for(....
			//if (!fs.existsSync(localFile)) {
			//	Log.warn("illegal entry: "+localFile);
			//	continue;
			//}		
			aggregateFileList(builder, targetFile, localFileList, readFile, function(err) {
				if (err) {
					callback(err);
				} else {
					buildEnd(builder, targetFile, resultUriList, callback);
				}
			});
		}
	});
}

function buildStart(assembler, readFile, callback) {
	assembler.startTime = new Date().getTime();
	assembler.emit('begin');
	assembler.emit('log','info','build begin for: '+assembler.config.linkTarget);
	if (assembler.config.downloadForce) {
		assembler.emit('log','info','build using forced downloads.');
	}
	var targetFile = mapLocalFileSync(assembler, assembler.config.linkTarget);
	fs.ensureFile(targetFile, function (err) {
		if (err) {
			callback(err);
		} else {
			assembler.emit('file-write-pre',targetFile);
			fs.writeFile(targetFile, assembler.config.assetHeader, function(err) {
				if (err) {
					callback(err);
				} else {
					buildAsset(assembler, targetFile, readFile, callback);
				}
			});
		}
	});
}

function runAssembler(assembler, readFile, callback) {
	if (assembler.config.downloadStartDelay) {
		setTimeout(function() {
			buildStart(assembler, readFile, callback);
		}, assembler.config.downloadStartDelay);
	} else {
		buildStart(assembler, readFile, callback);
	}
}

function runAssemblerSafe(assembler, readFile, callback) {
	runAssembler(assembler, readFile, function(err) {
		// send error
		if (err) {
			assembler.emit('error',err);
		}
		// finish callback
		if (callback !== undefined) {
			callback(err);
		}
	});	
}

function AssetAssembler(config, readFile) {
	this.config = config;
	this.startTime = 0;
	this.readFile = readFile || factory.assembler.constructor.readFile();
	events.EventEmitter.call(this);
}

AssetAssembler.prototype.__proto__ = events.EventEmitter.prototype;

AssetAssembler.prototype.run = function(callback) {
	if (callback === undefined) {
		throw new Error('no callback');
	}
	var self = this;
	config.checkConfig(self.config,function(err) {
		if (err) {
			callback(err);
		} else {
			config.fillDefaults(self.config, function (err) {
				if (err) {
					callback(err);
				} else {
					runAssemblerSafe(self, self.readFile, callback);
				}
			});
		}
	});
};

module.exports = AssetAssembler;