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

uson_text = { SOI ~ expr* ~ EOI }

expr = { value }

// Values
value = {
    typed
    | false_val
    | null_val
    | true_val
    | assign
    | object
    | array
    | number
    | string
}

false_val = { "false" }
null_val = { "null" }
true_val = { "true" }

// Objects - support optional commas like arrays
object = {
    "{" ~ (member ~ (","? ~ member)* ~ ","?)? ~ "}"
}

member = { string ~ ":" ~ value }

// Arrays
array = {
    "[" ~ (value ~ (","? ~ value)* ~ ","?)? ~ "]"
}

// Numbers - must not be followed by alphanumeric to avoid matching "1ab" as number
number = @{
    "-"? ~ int ~ ("." ~ ASCII_DIGIT+)? ~ (^"e" ~ ("+" | "-")? ~ ASCII_DIGIT+)? ~ !ASCII_ALPHANUMERIC
}

int = { "0" | (ASCII_NONZERO_DIGIT ~ ASCII_DIGIT*) }

// Strings
string = {
    double_quoted_string
    | single_quoted_string
    | unquoted_string
}

double_quoted_string = @{
    "\"" ~ (escape_sequence | (!("\"" | "\\") ~ ANY))* ~ "\""
}

single_quoted_string = @{
    "'" ~ (escape_sequence | (!("'" | "\\") ~ ANY))* ~ "'"
}

unquoted_string = @{
    simple_char+
}

simple_char = {
    !("\"" | "#" | "," | ":" | "[" | "\\" | "]" | "{" | "}" | WHITESPACE) ~ ANY
}

escape_sequence = @{
    "\\" ~ (
        "\"" | "'" | "\\" | "/" | "#"
        | "b" | "f" | "n" | "r" | "t"
        | ("u" ~ ASCII_HEX_DIGIT{4})
    )
}

// Assignments
assign = { string ~ ":" ~ value }

// Typed literals
typed = { type_name ~ "!" ~ value }
type_name = @{ (ASCII_ALPHA | ASCII_DIGIT | "_" | "-")+ }