Core Concepts

Core Concepts

Time Representation Rules

ℹ️ Note
This is a capability invariant.

• Internal manager unit: seconds
• Fractional seconds: allowed
• Player contract I/O: seconds
• Hook/module state exchange: seconds
• UI formatting/parsing happens at edges only (e.g., HH:MM:SS.mmm)
• Manager must never store milliseconds, frame numbers, or timecode strings

TrimRange

Represents selected media interval:

• startTime
• endTime
• Derived: duration = endTime - startTime

TrimState

Represents manager-owned capability state:

• initialRange
• current range
• videoDuration
• validation
• history (single-level in v1.1)

Selection Engine

Owns deterministic range transitions:

• setStartTime
• setEndTime
• moveRange
• reset
• undo

Validation Engine

Guarantees legal ranges:

• startTime >= 0
• endTime <= videoDuration
• startTime < endTime

⚠️ Warning
Validation failure must preserve prior valid range.

History Engine

v1.1 model:

• single previous snapshot
• reset() saves current range to history before reset
• undo() restores the previous snapshot once

Playback Sync Engine

Ensures preview behavior respects selected range:

• at/after endTime → pause
• seek back to startTime

ℹ️ Note
Sync behavior is evaluated against player time updates, not UI events.