WHITESPACE = _{ " " | "\t" | "\r" | "\n" }
COMMENT    = _{ "//" ~ (!"\n" ~ ANY)* }

program = { SOI ~ top_level* ~ EOI }

// primitives
identifier = @{ (ASCII_ALPHA | "_") ~ (ASCII_ALPHANUMERIC | "_")* }
integer    = @{ ASCII_DIGIT+ }
float      = @{ ASCII_DIGIT+ ~ "." ~ ASCII_DIGIT+ }
boolean    =  { "true" | "false" }
string_lit =  { "\"" ~ inner_str ~ "\"" }
inner_str  = @{ (!"\"" ~ ANY)* }

// ================= TOP LEVEL =================

top_level = _{ import | function_decl | struct_decl }

export = { "export" }

import = { "import" ~ string_lit ~ ";" }

param_list = { param ~ ("," ~ param)* ~ ","? }
param      = { identifier ~ ":" ~ type_expr }

struct_decl = {
    export? ~ "struct" ~ identifier ~ "{" ~ param_list? ~ "}"
}

function_decl = {
    export? ~ "function" ~ identifier ~ "(" ~ param_list? ~ ")" ~ (":" ~ type_expr)? ~ block
}

// ================= STATEMENTS =================

block = { "{" ~ statement_list ~ "}" }

statement_list = { statement* }

statement = _{ expr_stmt }

expr_stmt = { expr ~ ";" }

// ================= EXPRESSIONS =================
type_expr = { identifier }

primary = {
    integer
  | float
  | boolean
  | string_lit
  | identifier
}

postfix = {
    ("." ~ identifier)
  | ("(" ~ (expr ~ ("," ~ expr)*)? ~ ")")
}

expr = {
    primary ~ postfix*
}