CREATE TABLE IF NOT EXISTS source_scans (
    id VARCHAR(64) PRIMARY KEY,
    source_connection_id VARCHAR(64) NOT NULL REFERENCES source_connections(id) ON DELETE RESTRICT,
    source_type VARCHAR(32) NOT NULL CHECK (source_type IN ('pp', 'alist', 'dingtalk', 'manual')),
    state VARCHAR(16) NOT NULL CHECK (state IN ('pending', 'running', 'completed', 'failed')),
    snapshot_sha256 VARCHAR(64) NOT NULL DEFAULT '' CHECK (snapshot_sha256 = '' OR snapshot_sha256 ~ '^[0-9a-f]{64}$'),
    observed_items INTEGER NOT NULL DEFAULT 0 CHECK (observed_items >= 0),
    unchanged_items INTEGER NOT NULL DEFAULT 0 CHECK (unchanged_items >= 0),
    added_items INTEGER NOT NULL DEFAULT 0 CHECK (added_items >= 0),
    updated_items INTEGER NOT NULL DEFAULT 0 CHECK (updated_items >= 0),
    over_limit_items INTEGER NOT NULL DEFAULT 0 CHECK (over_limit_items >= 0),
    missing_items INTEGER NOT NULL DEFAULT 0 CHECK (missing_items >= 0),
    planned_uploads INTEGER NOT NULL DEFAULT 0 CHECK (planned_uploads >= 0),
    error_code VARCHAR(64) NOT NULL DEFAULT '',
    started_at TIMESTAMPTZ,
    completed_at TIMESTAMPTZ,
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
);

CREATE UNIQUE INDEX IF NOT EXISTS idx_source_scans_one_active
    ON source_scans (source_connection_id)
    WHERE state IN ('pending', 'running');

CREATE INDEX IF NOT EXISTS idx_source_scans_connection_created
    ON source_scans (source_connection_id, created_at DESC, id DESC);

CREATE TABLE IF NOT EXISTS source_scan_changes (
    id VARCHAR(64) PRIMARY KEY,
    source_scan_id VARCHAR(64) NOT NULL REFERENCES source_scans(id) ON DELETE RESTRICT,
    source_connection_id VARCHAR(64) NOT NULL REFERENCES source_connections(id) ON DELETE RESTRICT,
    stable_external_id VARCHAR(512) NOT NULL,
    source_item_id VARCHAR(64) REFERENCES source_items(id) ON DELETE RESTRICT,
    change_type VARCHAR(16) NOT NULL CHECK (change_type IN ('added', 'updated', 'unavailable')),
    previous_revision VARCHAR(512) NOT NULL DEFAULT '',
    observed_revision VARCHAR(512) NOT NULL DEFAULT '',
    observed_size_bytes BIGINT CHECK (observed_size_bytes IS NULL OR observed_size_bytes >= 0),
    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    UNIQUE (source_scan_id, stable_external_id)
);

CREATE INDEX IF NOT EXISTS idx_source_scan_changes_pending
    ON source_scan_changes (source_connection_id, change_type, created_at DESC, id DESC);