Small fixes in init.sql and create drop.sql

sql/init.sql

@@ -1,34 +1,74 @@
-CREATE TABLE election (
+CREATE TABLE elections (
     id INTEGER PRIMARY KEY AUTOINCREMENT,
     name TEXT NOT NULL,
     tokens INTEGER NOT NULL,
-    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
+    is_anonymous INTEGER NOT NULL,
+    max_voters INTEGER, -- mandatory when election is anonymous
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    expires_at DATETIME NOT NULL,
+    CHECK (is_anonymous = 0 OR (is_anonymous = 1 AND max_voters IS NOT NULL AND max_voters >= 1))
 );
 
+CREATE TRIGGER prevent_created_at_update_election
+    BEFORE UPDATE OF created_at ON elections
+BEGIN
+    SELECT RAISE(FAIL, 'created_at column is read-only');
+END;
+
 CREATE TABLE choices (
     text TEXT NOT NULL,
     election_id INTEGER NOT NULL,
     PRIMARY KEY (text, election_id),
-    FOREIGN KEY (election_id) REFERENCES election (id)
+    FOREIGN KEY (election_id) REFERENCES elections (id)
 );
 
 CREATE TABLE voters (
-    passcode TEXT NOT NULL,
+    identity TEXT NOT NULL, -- when election is anonymous, passcodes will be pre-generated
     election_id INTEGER NOT NULL,
-    PRIMARY KEY (passcode, election_id),
-    FOREIGN KEY (election_id) REFERENCES election (id)
+    PRIMARY KEY (identity, election_id),
+    FOREIGN KEY (election_id) REFERENCES elections (id)
 );
 
+CREATE TRIGGER enforce_max_voters
+    BEFORE INSERT ON voters
+    WHEN EXISTS (
+        SELECT 1
+        FROM elections e
+        WHERE e.id = NEW.election_id
+          AND e.max_voters IS NOT NULL
+    )
+BEGIN
+    SELECT CASE
+        WHEN (
+            SELECT COUNT(*)
+            FROM voters v
+            WHERE v.election_id = NEW.election_id
+        ) >= (
+            SELECT max_voters
+            FROM elections
+            WHERE id = NEW.election_id
+        )
+       THEN RAISE(FAIL, 'Maximum number of voters reached for this election')
+    END;
+END;
+
 CREATE TABLE votes (
-    voter_passcode TEXT NOT NULL,
+    voter_identity TEXT NOT NULL,
     election_id INTEGER NOT NULL,
-    choice_text TEXT NOT NULL,
-    tokens INTEGER NOT NULL,
-    calculated_vote_count GENERATED ALWAYS AS (sqrt(tokens)) VIRTUAL,
+    choice_text TEXT,
+    tokens INTEGER,
+    calculated_vote_count GENERATED ALWAYS AS (floor(sqrt(tokens))) VIRTUAL,
     created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
-    PRIMARY KEY (voter_passcode, choice_text),
-    FOREIGN KEY (voter_passcode, election_id) REFERENCES voters (passcode, election_id),
-    FOREIGN KEY (choice_text, election_id) REFERENCES choices (text, election_id)
+    PRIMARY KEY (voter_identity, choice_text),
+    FOREIGN KEY (voter_identity, election_id) REFERENCES voters (identity, election_id),
+    FOREIGN KEY (choice_text, election_id) REFERENCES choices (text, election_id),
+    CHECK (tokens IS NULL OR tokens >= 0)
 );
 
+CREATE TRIGGER prevent_created_at_update_votes
+    BEFORE UPDATE OF created_at ON votes
+BEGIN
+    SELECT RAISE(FAIL, 'created_at column is read-only');
+END;
+
 PRAGMA foreign_keys = ON; -- run after opening the connection so foreign key constraints are checked