meta:
  id: ovmb
  title: OVMB (OpenVolumeMesh binary file format)
  file-extension:
    - ovmb
  license: CC0-1.0
  encoding: ASCII
  endian: le
doc:
  OVMB files describe volumetric meshes and associated properties.
doc-ref: http://openvolumemesh.org
seq:

  - id: file_header
    type: file_header
  - id: chunks
    type: chunk
    repeat: eos

enums:
    int_encoding:
        0: none
        1: u8
        2: u16
        4: u32
    vertex_encoding:
        0: none
        1: float
        2: double
    property_entity:
        0: vertex
        1: edge
        2: face
        3: cell
        4: halfedge
        5: halfface
        6: mesh
    topo_type:
        0: polyhedral
        1: tetrahedral
        2: hexahedral
    topo_entity:
        1: edge
        2: face
        3: cell
types:
  file_header:
    seq:
      - id: magic
        contents: ['O', 'V', 'M', 'B', 0xa, 0xd, 0xa, 0xff]
      - id: file_version
        type: u1
      - id: header_version
        type: u1
      - id: vertex_dim
        type: u1
      - id: topo_type
        type: u1
        enum: topo_type
      - id: reserved
        contents: [0, 0, 0, 0]
      - id: n_vertices
        type: u8
      - id: n_edges
        type: u8
      - id: n_faces
        type: u8
      - id: n_cells
        type: u8
  chunk:
    seq:
      - id: type
        type: str
        size: 4
      - id: version
        type: u1
      - id: padding_bytes
        type: u1
      - id: compression
        type: u1
      - id: flags
        type: u1
      - id: file_length
        type: u8
      - id: body
        size: file_length - padding_bytes
        type:
            switch-on: type
            cases:
                '"VERT"': vert_chunk
                '"PROP"': prop_chunk
                '"TOPO"': topo_chunk
                '"DIRP"': propdir_chunk
      - id: padding
        size: padding_bytes
  array_span:
    seq:
      - id: base
        type: u8
      - id: count
        type: u4

  vert_chunk:
    seq:
      - id: span
        type: array_span
      - id: vertex_encoding
        type: u1
        enum: vertex_encoding
      - id: reserved
        contents: [0, 0, 0]
      - id: coordinates
        repeat: expr
        repeat-expr: span.count * _root.file_header.vertex_dim
        type:
          switch-on: vertex_encoding
          cases:
            'vertex_encoding::float': f4
            'vertex_encoding::double': f8

  topo_chunk:
    seq:
      - id: span
        type: array_span

      - id: entity
        type: u1
        enum: topo_entity

      - id: valence
        type: u1
        doc: 0 for variable valence

      - id: valence_encoding
        type: u1
        enum: int_encoding

      - id: handle_encoding
        type: u1
        enum: int_encoding

      - id: handle_offset
        type: u8

      - id: data
        type:
          switch-on: valence
          cases:
            0: topo_data_variable
            _: topo_data_fixed

  topo_data_fixed:
    seq:
      - id: handles
        repeat: expr
        repeat-expr: _parent.span.count * _parent.valence
        type:
          switch-on: _parent.handle_encoding
          cases:
            'int_encoding::u8': u1
            'int_encoding::u16': u2
            'int_encoding::u32': u4


  topo_data_variable:
    seq:
      - id: valences
        repeat: expr
        repeat-expr: _parent.span.count
        type:
          switch-on: _parent.valence_encoding
          cases:
            'int_encoding::u8': u1
            'int_encoding::u16': u2
            'int_encoding::u32': u4
      - id: handles
        type:
          switch-on: _parent.handle_encoding
          cases:
            'int_encoding::u8': u1
            'int_encoding::u16': u2
            'int_encoding::u32': u4

  propdir_chunk:
    seq:
      - id: entry
        type: propdir_entry
        repeat: eos

  string4:
    seq:
      - id: len
        type: u4
      - id: str
        type: str
        encoding: UTF-8
        size: len

  bytes4:
    seq:
      - id: len
        type: u4
      - id: data
        size: len

  propdir_entry:
    seq:
      - id: entity
        type: u1
        enum: property_entity
      - id: name
        type: string4
      - id: data_type_name
        type: string4
      - id: serialized_default
        type: bytes4

  prop_chunk:
    seq:
      - id: span
        type: array_span
      - id: prop_idx
        type: u4
      - id: data
        size-eos: true