Class DataLayer

Logical index of the latest real bar (length - 1), or -1 if empty.

Number of logical indices (distinct time points across all series).

Upsert bars into a series by time (used for history paging / backfill / out-of-order corrections — ARCHITECTURE.md §4.2). Existing times are replaced; new times are inserted; the result stays time-sorted.

Prepending older bars shifts every existing logical index up by the inserted count — callers preserve the viewport by re-reading baseIndex (the invariant rightEdge − index is unchanged, so visible bars don't move).

Register a new series; returns its id.

All bars of a series paired with their shared logical index.

Fractional logical index → UTC seconds, interpolating between bars and extrapolating past either edge at the nearest bar spacing.

indexToTime only answers for indices that have a bar. Anything anchored to an arbitrary x — a drawing endpoint, a cursor readout, a projection to the right of the last bar — needs a time for positions between bars too, which the gapless axis (§5.3) makes common: everything a weekend or a session break collapsed away lands there. Returns NaN when there is no data.

The last bar of a series with its shared logical index, in O(1).

A series' bars, time-sorted, with no per-call allocation — the read path for anything that recomputes over full history (indicators, transforms). The array is live: treat it as read-only.

Bulk-load (full replace) one series' data, then re-merge the time axis. Input is sorted and de-duplicated by time by a private sortedUniqueByTime.

UTC seconds → fractional logical index. The inverse of indexToTimeFloat.

Apply a single live bar (ARCHITECTURE.md §4.2 hot path). Returns the kind of change so the chart auto-scrolls only on a genuine right-edge append:

• 'append' → newer than the last bar (advances baseIndex)
• 'replace' → same time as the last bar (intra-bar tick) or an existing time
• 'insert' → an older time inserted into history (late / out-of-order)

Bars of a series whose logical index lies within [fromIndex, toIndex]. Binary-searches the (time-sorted) series into the visible time window instead of scanning all bars, so a full repaint costs O(log n + visible) per series, not O(total bars) - the hot path called for autoscale and drawing every frame.