include "sst.fbs";

table Uuid {
   high: uint64;
   low: uint64;
}

// Manifest to persist state of DB.
table ManifestV1 {
    // Id of manifest. Manifest file name will be derived from this id.
    manifest_id: ulong;

    // Flag to indicate whether initialization has finished. When creating the initial manifest for
    // a root db (one that is not a clone), this flag will be set to true. When creating the initial
    // manifest for a clone db, this flag will be set to false and then updated to true once clone
    // initialization has completed.
    initialized: bool;

    // The current writer's epoch.
    writer_epoch: ulong;

    // The current compactor's epoch.
    compactor_epoch: ulong;

    // The most recent SST in the WAL that's been compacted.
    wal_id_last_compacted: ulong;

    // The most recent SST in the WAL at the time manifest was updated.
    wal_id_last_seen: ulong;

    // The last compacted l0
    l0_last_compacted: CompactedSstId;

    // A list of the L0 SSTs that are valid to read in the `compacted` folder.
    l0: [CompactedSsTable] (required);

    // A list of the sorted runs that are valid to read in the `compacted` folder.
    compacted: [SortedRun] (required);

    // The last clock tick
    last_clock_tick: long;

    // A list of checkpoints that are currently open.
    checkpoints: [Checkpoint] (required);
}

table SortedRun {
    id: uint32;
    ssts: [CompactedSsTable] (required);
}

table WriterCheckpoint {
   epoch: uint64;
}

union CheckpointMetadata { WriterCheckpoint }

// Checkpoint reference to be included in manifest to record active checkpoints.
table Checkpoint {
    // Id that must be unique across all open checkpoints.
    id: Uuid (required);

    // The manifest ID that this checkpoint is using as its `DbState`.
    manifest_id: ulong;

    // The UTC unix timestamp seconds that a checkpoint expires at. Clients may update this value.
    // If `checkpoint_expire_time_s` is older than now(), the checkpoint is considered expired.
    // If `checkpoint_expire_time_s` is 0, the checkpoint will never expire.
    checkpoint_expire_time_s: uint;

    // The unix timestamp seconds that the checkpoint was created
    checkpoint_create_time_s: uint;

    // Optional metadata associated with the checkpoint. For example, the writer can use this to
    // clean up checkpoints from older writers.
    metadata: CheckpointMetadata;
}