Working on reading the body

src/body.jl

@@ -1,27 +1,29 @@
-"""
-read the body of the FIT file.
-"""
 module body
 
 # TODO: Why do this?
 import Base.show
 
-export RecordHeader, read_row
+export DefinitionHeader, DataRecord, read_row
 
 include("bytes.jl"); using.bytes
 include("mesg_num.jl"); using .mesg_num
 
-struct DefinitionMessage end
-struct DataMessage end
 
-"""
-    RecordHeader
+struct DefinitionHeader
+    endianness::AbstractString
+    number::Int64
+    fields::UInt8 
+end
 
-The byte that corresponds to the type of message that this record holds.
-"""
-struct RecordHeader
-    definition_message::Bool
-    timestamp_message::Bool
+# 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
 
 
@@ -31,17 +33,44 @@ end
 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)
+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
-    RecordHeader(
-        bit_at(header_byte, 2),
-        bit_at(header_byte, 1))
+    # 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 show(io::IO, header::RecordHeader)
-    println(io, header.definition_message ? "DefinitionMessage" : "DataMessage")
+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

src/file.jl

@@ -10,7 +10,7 @@ using .body
 
 struct FITFile
     header::FITHeader
-    body::RecordHeader
+    body::DefinitionHeader
 end
 
 function read_file(filepath::AbstractString)::FITFile

src/mesg_num.jl

@@ -2,6 +2,8 @@
 
 module mesg_num
 
+export get_mesg_num_string, get_field_definition_string
+
 FILE_ID = 0
 CAPABILITIES = 1
 DEVICE_SETTINGS = 2
@@ -202,7 +204,7 @@ MESG_NUM_MAP = Dict(
 
 Given the number from our data record, get a string label. Nothing if not found.
 """
-function get_mesg_num_string(mesg_num::Integer)::Union{AbstractString,Nothing}
+function get_mesg_num_string(mesg_num::Real)::Union{AbstractString,Nothing}
     try
         MESG_NUM_MAP[mesg_num]
     catch e
@@ -214,4 +216,18 @@ function get_mesg_num_string(mesg_num::Integer)::Union{AbstractString,Nothing}
     end
 end
 
+FIELD_DEFINITION_MAP = Dict(
+    0xFF => "Invalid",
+    254 => "MessageIndex",
+    253 => "Timestamp",
+    250 => "PartNumber"
+)
+function get_field_definition_string(num::Real)::Union{AbstractString,Nothing}
+    try
+        FIELD_DEFINITION_MAP[num]
+    catch e
+        nothing
+    end
+end
+
 end