-- Migration 008: FTS5 Full-Text Search Index
-- Schema version: 8
-- Adds full-text search on documents table with sync triggers

-- Full-text search with porter stemmer and prefix indexes for type-ahead
CREATE VIRTUAL TABLE documents_fts USING fts5(
  title,
  content_text,
  content='documents',
  content_rowid='id',
  tokenize='porter unicode61',
  prefix='2 3 4'
);

-- Keep FTS in sync via triggers.
-- IMPORTANT: COALESCE(title, '') ensures FTS5 external-content table never
-- receives NULL values, which can cause inconsistencies with delete operations.
-- FTS5 delete requires exact match of original values; NULL != NULL in SQL,
-- so a NULL title on insert would make the delete trigger fail silently.
CREATE TRIGGER documents_ai AFTER INSERT ON documents BEGIN
  INSERT INTO documents_fts(rowid, title, content_text)
  VALUES (new.id, COALESCE(new.title, ''), new.content_text);
END;

CREATE TRIGGER documents_ad AFTER DELETE ON documents BEGIN
  INSERT INTO documents_fts(documents_fts, rowid, title, content_text)
  VALUES('delete', old.id, COALESCE(old.title, ''), old.content_text);
END;

-- Only rebuild FTS when searchable text actually changes (not metadata-only updates)
CREATE TRIGGER documents_au AFTER UPDATE ON documents
WHEN old.title IS NOT new.title OR old.content_text != new.content_text
BEGIN
  INSERT INTO documents_fts(documents_fts, rowid, title, content_text)
  VALUES('delete', old.id, COALESCE(old.title, ''), old.content_text);
  INSERT INTO documents_fts(rowid, title, content_text)
  VALUES (new.id, COALESCE(new.title, ''), new.content_text);
END;

-- Update schema version
INSERT INTO schema_version (version, applied_at, description)
VALUES (8, strftime('%s', 'now') * 1000, 'FTS5 full-text search index with sync triggers');