# This Pest grammar defines the syntax for filter chains used in the Keep application.
# Filters can be chained with commas and may have named or unnamed options with JSON-like values.

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

# Top-level rule for parsing multiple filters separated by commas.
filters = { filter ~ ("," ~ filters)? }

# A single filter consisting of a name optionally followed by parenthesized options.
filter = { filter_name ~ ("(" ~ options ~ ")")? }

# The name of a filter, starting with an ASCII letter followed by alphanumeric characters or underscores.
filter_name = @{ ASCII_ALPHA ~ (ASCII_ALPHANUMERIC | "_")* }

# A list of comma-separated options within parentheses.
options = { option ~ ("," ~ options)? }

# A single option, optionally with a name followed by an equals sign and a value.
option = { (option_name ~ "=")? ~ option_value }

# The name of an option, starting with an ASCII letter followed by alphanumeric characters or underscores.
option_name = @{ ASCII_ALPHA ~ (ASCII_ALPHANUMERIC | "_")* }

# The value of an option, which can be a JSON number, string, or boolean.
option_value = { 
    JSON_NUMBER |
    JSON_STRING |
    JSON_BOOLEAN
}

# JSON number format supporting integers, decimals, and scientific notation.
JSON_NUMBER = @{ 
    ("-")? ~ 
    ("0" | ASCII_NONZERO_DIGIT ~ ASCII_DIGIT*) ~ 
    ("." ~ ASCII_DIGIT*)? ~ 
    (("e" | "E") ~ ("+" | "-")? ~ ASCII_DIGIT+)? 
}

# JSON string format with escaped characters.
JSON_STRING = ${ 
    "\"" ~ 
    (("\\" ~ ANY) | (!("\"" | "\\") ~ ANY))* ~ 
    "\"" 
}

# JSON boolean values: true or false.
JSON_BOOLEAN = ${ "true" | "false" }