// Copyright 2021-2024 The Jujutsu Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

whitespace = _{ " " | "\t" | "\r" | "\n" | "\x0c" }

// XID_CONTINUE: https://www.unicode.org/reports/tr31/#Default_Identifier_Syntax
// +, -, ., @, _: commonly used in file name including "." and ".."
// *, ?, [, ]: glob characters (not extended glob)
// /: path separator
// \: path separator (Windows)
identifier = @{
  (XID_CONTINUE | "+" | "-" | "." | "@" | "_" | "*" | "?" | "[" | "]" | "/" | "\\")+
}
strict_identifier_part = @{ (ASCII_ALPHANUMERIC | "_")+ }
strict_identifier = @{
  strict_identifier_part ~ ("-" ~ strict_identifier_part)*
}

// TODO: accept more ASCII meta characters such as "#" and ","?
bare_string = @{
  ( ASCII_ALPHANUMERIC
  | " " | "+" | "-" | "." | "@" | "_" | "*" | "?" | "[" | "]" | "/" | "\\"
  | '\u{80}'..'\u{10ffff}' )+
}

string_escape = @{ "\\" ~ ("t" | "r" | "n" | "0" | "\"" | "\\") }
string_content_char = @{ !("\"" | "\\") ~ ANY }
string_content = @{ string_content_char+ }
string_literal = ${ "\"" ~ (string_content | string_escape)* ~ "\"" }

raw_string_content = @{ (!"'" ~ ANY)* }
raw_string_literal = ${ "'" ~ raw_string_content ~ "'" }

pattern_kind_op = { ":" }

negate_op = { "~" }
union_op = { "|" }
intersection_op = { "&" }
difference_op = { "~" }
prefix_ops = _{ negate_op }
infix_ops = _{ union_op | intersection_op | difference_op }

function = { function_name ~ "(" ~ whitespace* ~ function_arguments ~ whitespace* ~ ")" }
function_name = @{ (ASCII_ALPHANUMERIC | "_")+ }
function_arguments = {
  expression ~ (whitespace* ~ "," ~ whitespace* ~ expression)* ~ (whitespace* ~ ",")?
  | ""
}

// TODO: change rhs to string_literal to require quoting? #2101
string_pattern = {
  strict_identifier
  ~ pattern_kind_op
  ~ (identifier | string_literal | raw_string_literal)
}
bare_string_pattern = { strict_identifier ~ pattern_kind_op ~ bare_string }

primary = {
  "(" ~ whitespace* ~ expression ~ whitespace* ~ ")"
  | function
  | string_pattern
  | identifier
  | string_literal
  | raw_string_literal
}

expression = {
  (prefix_ops ~ whitespace*)* ~ primary
  ~ (whitespace* ~ infix_ops ~ whitespace* ~ (prefix_ops ~ whitespace*)* ~ primary)*
}

program = _{ SOI ~ whitespace* ~ expression ~ whitespace* ~ EOI }
program_or_bare_string = _{
  SOI ~ ( whitespace* ~ expression ~ whitespace* ~ EOI
        | bare_string_pattern ~ EOI
        | bare_string ~ EOI )
}