CREATE TABLE IF NOT EXISTS schema_versions(version INTEGER PRIMARY KEY, applied_at TEXT NOT NULL);
CREATE TABLE IF NOT EXISTS operators(
 id TEXT PRIMARY KEY, username TEXT UNIQUE NOT NULL, password_hash TEXT NOT NULL, created_at TEXT NOT NULL
);
CREATE TABLE IF NOT EXISTS auth_sessions(
 token_hash TEXT PRIMARY KEY, operator_id TEXT REFERENCES operators(id), csrf TEXT NOT NULL,
 expires_at BIGINT NOT NULL, created_at TEXT NOT NULL
);
CREATE TABLE IF NOT EXISTS auth_attempts(key TEXT PRIMARY KEY, failures INTEGER NOT NULL, window_start BIGINT NOT NULL);
CREATE TABLE IF NOT EXISTS learning_tasks(
 id TEXT PRIMARY KEY, owner_id TEXT NOT NULL REFERENCES operators(id), name TEXT NOT NULL,
 platform TEXT NOT NULL, entry_url TEXT NOT NULL, goal TEXT NOT NULL, account_key TEXT NOT NULL,
 parameters_json TEXT NOT NULL, status TEXT NOT NULL, identity_label TEXT,
 created_at TEXT NOT NULL, updated_at TEXT NOT NULL,
 ordinal BIGINT GENERATED ALWAYS AS IDENTITY UNIQUE
);
CREATE TABLE IF NOT EXISTS observations(
 id TEXT PRIMARY KEY, task_id TEXT NOT NULL REFERENCES learning_tasks(id), data_json TEXT NOT NULL,
 created_at TEXT NOT NULL, ordinal BIGINT GENERATED ALWAYS AS IDENTITY UNIQUE
);
CREATE INDEX IF NOT EXISTS observations_task ON observations(task_id,ordinal);
CREATE TABLE IF NOT EXISTS learning_steps(
 id TEXT PRIMARY KEY, task_id TEXT NOT NULL REFERENCES learning_tasks(id), position INTEGER NOT NULL,
 data_json TEXT NOT NULL, created_at TEXT NOT NULL, UNIQUE(task_id,position)
);
CREATE TABLE IF NOT EXISTS candidates(
 id TEXT PRIMARY KEY, task_id TEXT NOT NULL REFERENCES learning_tasks(id), name TEXT NOT NULL,
 version INTEGER NOT NULL, digest TEXT NOT NULL, manifest_json TEXT NOT NULL, created_at TEXT NOT NULL,
 ordinal BIGINT GENERATED ALWAYS AS IDENTITY UNIQUE, UNIQUE(task_id,version)
);
CREATE TABLE IF NOT EXISTS validations(
 id TEXT PRIMARY KEY, candidate_id TEXT NOT NULL REFERENCES candidates(id), task_id TEXT NOT NULL REFERENCES learning_tasks(id),
 kind TEXT NOT NULL, status TEXT NOT NULL, data_json TEXT NOT NULL, created_at TEXT NOT NULL,
 ordinal BIGINT GENERATED ALWAYS AS IDENTITY UNIQUE
);
CREATE INDEX IF NOT EXISTS validations_candidate ON validations(candidate_id,ordinal);
CREATE TABLE IF NOT EXISTS artifacts(
 id TEXT PRIMARY KEY, task_id TEXT NOT NULL REFERENCES learning_tasks(id), relative_path TEXT NOT NULL,
 sha256 TEXT NOT NULL, bytes BIGINT NOT NULL, created_at TEXT NOT NULL
);
CREATE OR REPLACE FUNCTION reject_learning_fact_mutation() RETURNS TRIGGER
LANGUAGE plpgsql AS $guard$
BEGIN
 RAISE EXCEPTION 'learning facts are immutable and append only' USING ERRCODE='23514';
END;
$guard$;