-- Migration 016: MR file changes table
-- Powers file-history and trace commands (Gates 4-5)

CREATE TABLE mr_file_changes (
    id INTEGER PRIMARY KEY,
    merge_request_id INTEGER NOT NULL REFERENCES merge_requests(id) ON DELETE CASCADE,
    project_id INTEGER NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
    old_path TEXT,
    new_path TEXT NOT NULL,
    change_type TEXT NOT NULL CHECK (change_type IN ('added', 'modified', 'renamed', 'deleted')),
    UNIQUE(merge_request_id, new_path)
);

CREATE INDEX idx_mfc_project_path ON mr_file_changes(project_id, new_path);
CREATE INDEX idx_mfc_project_old_path ON mr_file_changes(project_id, old_path) WHERE old_path IS NOT NULL;
CREATE INDEX idx_mfc_mr ON mr_file_changes(merge_request_id);
CREATE INDEX idx_mfc_renamed ON mr_file_changes(project_id, change_type) WHERE change_type = 'renamed';

INSERT INTO schema_version (version, applied_at, description)
VALUES (16, strftime('%s', 'now') * 1000, 'MR file changes table');