module body

# TODO: Why do this?
import Base.show

export DefinitionHeader, DataRecord, read_row

include("bytes.jl"); using.bytes
include("mesg_num.jl"); using .mesg_num


struct DefinitionHeader
    endianness::AbstractString
    number::Int64
    fields::UInt8 
end

# TODO: field_number has a string value, type has a Julia type.
struct DefinitionField
    field_number::AbstractString
    size::UInt8
    type::UInt8
end

struct DataRecord
    hdr::DefinitionHeader
end


"""
    read_row(f::io)

Read a row of the file at a time. Parse the row into a data or def message.
TODO: Endianness matters here. Need to resolve endianness with the architecture bit.
"""
function read_row(f::IO)::DefinitionHeader
    header_byte = read(f, 1; all=false)[1]

    definition_message = Bool(bit_at(header_byte, 2))
    # The message byte is 7
    # hdr = RecordHeader(
    #     Bool(bit_at(header_byte, 2)),
    #     Bool(bit_at(header_byte, 1)))
    # TODO: hdr if compressed timestamp needs to be handled in special way.
    
    if definition_message
        fixed_bytes = read(f, 5; all=false)
        hdr = DefinitionHeader(
            endianness(fixed_bytes[2]), byte_vec_to_int(fixed_bytes[3:4]), fixed_bytes[end] 
        )
    end
    hdr_fields = [hdr_field(read(f, 3; all=false)) for i ∈ 1:hdr.fields + 1]
    println(hdr_fields)
    hdr
end

function hdr_field(vec::Vector{UInt8})::DefinitionField
    println(vec)
    DefinitionField(
        get_mesg_num_string(vec[1]), vec[2], vec[3]
    )
end

function endianness(b::UInt8)::AbstractString
    Bool(b) ? "BigEndian" : "LittleEndian"
end

function show(io::IO, header::DefinitionHeader)
    print(io, "DefinitionHeader($(header.endianness), $(header.number), $(header.fields) messages)")
end

function show(io::IO, field::DefinitionField)
    print(io, "DefinitionField($(field.field_number), $(field.size), $(field.type))")
end

end