planout.pest

program = _{ SOI ~ stmt* ~ EOI }

stmt = _{ ret | expr }

expr = {
    assignment |  conditional | monadic_expr | dyadic_expr | terms
}

assignment = { ident ~ op_assign ~ expr ~ semi}
op_assign = { "=" }

terms = { term+ }

term = _{ string | boolean | ident | number | array | "(" ~ expr ~ ")" }



array_start = { "[" }
array_end = { "]" }
array = { array_start ~ (array_end | (expr ~ array_end) | ((expr ~ ",")* ~ expr ~ array_end))  }

op_bool_or = { "||" }
op_bool_and = { "&&" }
op_eq = { "==" }
op_ne = { "!=" }
op_ge = { ">=" }
op_le = { "<=" }
op_gt = { ">" }
op_lt = { "<" }

bool_not = _{ op_bool_not ~ expr }
op_bool_not = { "!" }

ret = { "return" ~ terms ~ semi }

product = { expr ~ "*" ~ expr }
addition = { expr ~ "+" ~ expr }
subtraction = { expr ~ "-" ~ expr }
sum = {  addition | subtraction }

monadic_expr = { verb ~ expr }

dyadic_expr = { (monadic_expr | terms) ~ verb ~ expr }

verb = {
    "+" | "*"
//    ">" | "*:" | "-"  | "%" | "#" | ">."
//  | "+"  | "*"  | "<"  | "=" | "^" | "|"
//  | ">"  | "$"
}



conditional = { 
    op_if ~ "(" ~ terms ~ ")" ~ block ~ 
    (op_else_if ~ "(" ~ terms ~ ")" ~ block)*
    ~ (op_else ~ block)? 
}

op_if = { "if" }
op_else_if = { "else if" }
op_else = { "else" }

block = _{ block_start ~ expr* ~ block_end }
block_start = { "{" }
block_end = { "}" }

field_access = { ident ~ op_access ~ ident  }
op_access = { "." }

boolean = @{ "true" | "false" }

ident = @{ ASCII_ALPHA ~ (ASCII_ALPHANUMERIC | "_")* }


number = { decimal | integer }

decimal = @{ "_"? ~ ASCII_DIGIT+ ~ "." ~ ASCII_DIGIT* }
integer = @{ "0" | (nonzero ~ digit*) }
// Allow "_" in numbers for grouping: 1_000_000 == 1000000
digit = _{ "0" | nonzero | "_" }
nonzero = _{ '1'..'9' }


string = ${ "\"" ~ string_inner ~ "\"" }
string_inner = @{ char* }
char = {
    !("\"" | "\\") ~ ANY
    | "\\" ~ ("\"" | "\\" | "/" | "b" | "f" | "n" | "r" | "t")
    | "\\" ~ ("u" ~ ASCII_HEX_DIGIT{4})
}

keyword = @{
    "else" | "false" | "if" | "return" | "switch" | "return"
}

semi = { ";" }

WHITESPACE = _{ " " | "\t" | "\r" | "\n" }