BLT editor: Implement BLT export

html/blt/index.html

@@ -29,7 +29,7 @@
 			<button onclick="clickOpenJSON()">Open JSON</button>
 			<button onclick="clickSaveJSON()">Save JSON</button>
 			<button onclick="clickImportBLT()">Import BLT</button>
-			<!--<button>Export BLT</button>-->
+			<button onclick="clickExportBLT()">Export BLT</button>
 			<!--GITREV-->
 			<a href="https://yingtongli.me/blog/2020/12/24/pyrcv2.html">Information and instructions</a>
 		</div>

html/blt/index.js

@@ -145,7 +145,7 @@ async function changeInpFile() {
 			
 			ballots = [];
 			for (let ballot of election.ballots) {
-				let js_ballot = {'value': ballot.value.impl, 'preferences': []};
+				let js_ballot = {'value': ballot.value.__str__(), 'preferences': []};
 				for (let i = 0; i < candidates.length; i++) {
 					js_ballot['preferences'].push('');
 				}
@@ -183,8 +183,62 @@ function clickSaveJSON() {
 		'ballots': ballots,
 	};
 	
+	// Download file
 	let url = URL.createObjectURL(new File([JSON.stringify(result)], 'ballots.json', {type: 'application/json'}));
+	let elA = document.createElement('a');
+	elA.href = url;
+	elA.download = '';
+	elA.click();
+}
 
+function clickExportBLT() {
+	let election = py.pyRCV2.model.Election();
+	
+	let result = window.prompt('Enter the number of seats to elect:', '1');
+	if (result !== null) {
+		election.seats = parseInt(result);
+	} else {
+		return;
+	}
+	
+	result = window.prompt('Enter the name of the election:');
+	if (result !== null) {
+		election.name = result;
+	} else {
+		return;
+	}
+	
+	for (let candidate of candidates) {
+		let py_candidate = py.pyRCV2.model.Candidate(candidate);
+		election.candidates.push(py_candidate);
+	}
+	
+	// Process ballots
+	for (let ballot of ballots) {
+		let py_ballot = py.pyRCV2.model.Ballot(py.pyRCV2.numbers.StringNum(ballot['value']), []);
+		
+		for (let i = 1; i < candidates.length + 1; i++) {
+			let candidate = null;
+			for (let j = 0; j < candidates.length; j++) {
+				if (ballot.preferences[j].trim() === '' + i) {
+					candidate = j;
+					break;
+				}
+			}
+			
+			if (candidate !== null) {
+				py_ballot.preferences.push(election.candidates[candidate]);
+			} else {
+				// No such preference
+				break;
+			}
+		}
+		
+		election.ballots.push(py_ballot);
+	}
+	
+	// Download file
+	let url = URL.createObjectURL(new File([py.pyRCV2.blt.writeBLT(election)], 'election.blt', {type: 'application/json'}));
 	let elA = document.createElement('a');
 	elA.href = url;
 	elA.download = '';

pyRCV2/blt.py

@@ -68,3 +68,26 @@ def readBLT(data):
 	election.withdrawn = [election.candidates[x] for x in withdrawn]
 	
 	return election
+
+def writeBLT(election, stringify=str):
+	lines = []
+	
+	lines.append('{} {}'.format(len(election.candidates), election.seats))
+	
+	if len(election.withdrawn) > 0:
+		lines.append(' '.join(['-{}'.format(election.candidates.index(candidate) + 1) for candidate in election.withdrawn]))
+	
+	for ballot in election.ballots:
+		if ballot.preferences:
+			lines.append('{} {} 0'.format(stringify(ballot.value), ' '.join(str(election.candidates.index(x) + 1) for x in ballot.preferences)))
+		else:
+			lines.append('{} 0'.format(stringify(ballot.value)))
+	
+	lines.append('0')
+	
+	for candidate in election.candidates:
+		lines.append('"{}"'.format(candidate.name))
+	
+	lines.append('"{}"'.format(election.name))
+	
+	return '\n'.join(lines)

pyRCV2/numbers/string_js.py

@@ -26,3 +26,6 @@ class StringNum(BaseNum):
 	def _to_impl(cls, value):
 		"""Implements BaseNum._to_impl"""
 		return value
+	
+	def __str__(self):
+		return self.impl