WHITESPACE = _{ " " | "\n" }
COMMENT = { block_comment | line_comment }

block_comment = { "/*" ~ (!"*/" ~ ANY)* ~ "*/" }
line_comment = { "//" ~ (!"\n" ~ ANY)* }

alpha = { 'a'..'z' | 'A'..'Z' }
digit = { '0'..'9' }
hexdigit = { digit | 'a'..'f' | 'A'..'F' }
alphanum = { alpha | digit | "_" }

identifier = @{ alpha ~ alphanum* }
payload_identifier = @{ "_payload_" }
body_identifier = @{ "_body_" }
intvalue = @{ digit+ }
hexvalue = @{ ("0x"|"0X") ~ hexdigit+ }
integer = @{ hexvalue | intvalue }
string = @{ "\"" ~ (!"\"" ~ ANY)* ~ "\"" }
size_modifier = @{
    ("+"|"-"|"*"|"/") ~ (digit|"+"|"-"|"*"|"/")+
}

endianness_declaration = { "little_endian_packets" | "big_endian_packets" }

enum_tag = { identifier ~ "=" ~ integer }
enum_tag_list = { enum_tag ~ ("," ~ enum_tag)* ~ ","? }
enum_declaration = {
    "enum" ~ identifier ~ ":" ~ integer ~ "{" ~
        enum_tag_list ~
    "}"
}

constraint = { identifier ~ "=" ~ (identifier|integer) }
constraint_list = { constraint ~ ("," ~ constraint)* }

checksum_field = { "_checksum_start_" ~ "(" ~ identifier ~ ")" }
padding_field = { "_padding_" ~ "[" ~ integer ~ "]" }
size_field = { "_size_" ~ "(" ~ (identifier|payload_identifier|body_identifier)  ~ ")" ~ ":" ~ integer }
count_field = { "_count_" ~ "(" ~ identifier ~ ")" ~ ":" ~ integer }
elementsize_field = { "_elementsize_" ~ "(" ~ identifier ~ ")" ~ ":" ~ integer }
body_field = @{ "_body_" }
payload_field = { "_payload_" ~ (":" ~ "[" ~ size_modifier ~ "]")? }
fixed_field = { "_fixed_" ~ "=" ~ (
    (integer ~ ":" ~ integer) |
    (identifier ~ ":" ~ identifier)
)}
reserved_field = { "_reserved_" ~ ":" ~ integer }
array_field = { identifier ~ ":" ~ (integer|identifier) ~
    "[" ~ (size_modifier|integer)? ~ "]"
}
scalar_field = { identifier ~ ":" ~ integer }
typedef_field = { identifier ~ ":" ~ identifier }
group_field = { identifier ~ ("{" ~ constraint_list ~ "}")? }

field = _{
    checksum_field |
    padding_field |
    size_field |
    count_field |
    elementsize_field |
    body_field |
    payload_field |
    fixed_field |
    reserved_field |
    array_field |
    scalar_field |
    typedef_field |
    group_field
}
field_list = { field ~ ("," ~ field)* ~ ","? }

packet_declaration = {
   "packet" ~ identifier ~
        (":" ~ identifier)? ~
           ("(" ~ constraint_list ~ ")")? ~
    "{" ~
        field_list? ~
    "}"
}

struct_declaration = {
    "struct" ~ identifier ~
        (":" ~ identifier)? ~
           ("(" ~ constraint_list ~ ")")? ~
    "{" ~
        field_list? ~
    "}"
}

group_declaration = {
    "group" ~ identifier ~ "{" ~ field_list ~ "}"
}

checksum_declaration = {
    "checksum" ~ identifier ~ ":" ~ integer ~ string
}

custom_field_declaration = {
    "custom_field" ~ identifier ~ (":" ~ integer)? ~ string
}

test_case = { string }
test_case_list = _{ test_case ~ ("," ~ test_case)* ~ ","? }
test_declaration = {
    "test" ~ identifier ~ "{" ~
        test_case_list ~
    "}"
}

declaration = _{
    enum_declaration |
    packet_declaration |
    struct_declaration |
    group_declaration |
    checksum_declaration |
    custom_field_declaration |
    test_declaration
}

file = {
    SOI ~
    endianness_declaration ~
    declaration* ~
    EOI
}