## Wire format for a single segment, per the Reliable Channel API spec.
##
## Skeleton: encode/decode treat the segment as just its payload bytes,
## since for now we only ever produce a single segment per send.

type SegmentMessageProto* = object
  entireMessageHash*: seq[byte] ## Keccak256(original payload), 32 bytes
  dataSegmentIndex*: uint32 ## zero-indexed sequence number for data segments
  dataSegmentCount*: uint32 ## number of data segments (>= 1)
  payload*: seq[byte] ## segment payload (data or parity shard)
  paritySegmentIndex*: uint32 ## zero-based sequence number for parity segments
  paritySegmentCount*: uint32 ## number of parity segments
  isParity*: bool ## true for parity segments, false (default) for data segments

proc isParityMessage*(self: SegmentMessageProto): bool =
  self.isParity

proc isValid*(self: SegmentMessageProto): bool =
  ## Validates hash length (32 bytes), segment indices and counts.
  discard

proc encode*(self: SegmentMessageProto): seq[byte] =
  self.payload

proc decode*(T: type SegmentMessageProto, buf: seq[byte]): T =
  T(
    entireMessageHash: @[],
    dataSegmentIndex: 0,
    dataSegmentCount: 1,
    payload: buf,
    paritySegmentIndex: 0,
    paritySegmentCount: 0,
    isParity: false,
  )