rmk-config 0.4.0

// Grammar for RMK keyboard.toml layer.keys string

// Define default whitespace handling (space, tab, newline, carriage return)
WHITESPACE = _{ " " | "\t" | "\n" | "\r" }

// Optional comments
COMMENT = _{ "//" ~ (!"\n" ~ ANY)* } 

// --- Helper Rules ---

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

// captures anything that isn't whitespace or a specific delimiter
loose_identifier = @{ (!( "(" | ")" | "," | "@" | WHITESPACE ) ~ ANY)+ }

keycode_name = @{ loose_identifier }

// Number (for layer indices)
number = @{ ASCII_DIGIT+ }

// Layer Reference (either a number or a name)
layer_number = @{ number }
layer_name = @{ loose_identifier }

//the order is important here, as we want to match the number first 
layer_reference = _{ layer_number | layer_name }

// Modifier Names
modifier_name = @{
    ^"LShift" | ^"LCtrl" | ^"LAlt" | ^"LGui" |
    ^"RShift" | ^"RCtrl" | ^"RAlt" | ^"RGui"
}

// Modifier Chain (one or more modifiers separated by '|')
// Silent rules (_) used for delimiters we don't need in the AST.
modifier_combination = { modifier_name ~ ("|" ~ modifier_name)* }

// --- Main Action Rules ---

// Rule 0: Simple Keycode (must come after more specific rules)
simple_keycode = { keycode_name }

// Rule 2: No Key
no_action = { ^"No" } // Case-insensitive "No"

// Rule 3: Transparent Key
transparent_action = @{ ("_")+ | ^"Trns" } // One or more 

// Rule 1: WM(key, modifier) - Key with Modifier
wm_action = { ^"WM" ~ "(" ~ keycode_name ~ "," ~ modifier_combination ~ ")" }

// Rule 4.6: OSM(modifier) - One-Shot Modifier (requires quotes)
osm_action = { ^"OSM" ~ "(" ~ "\"" ~ modifier_combination ~ "\"" ~ ")" }

// Rule 4.1: DF(n) - Switch Default Layer
df_action = { ^"DF" ~ "(" ~ layer_reference ~ ")" }

// Rule 4.2: MO(n) - Momentary Layer Activate
mo_action = { ^"MO" ~ "(" ~ layer_reference ~ ")" }

// Rule 4.3: LM(n, modifier) - Layer Activate with Modifier
lm_action = { ^"LM" ~ "(" ~ layer_reference ~ "," ~ modifier_combination ~ ")" }

// Rule 4.4: LT(n, key) - Layer Activate or Tap Key (Tap/Hold)
lt_action = { ^"LT" ~ "(" ~ layer_reference ~ "," ~ keycode_name ~ ")" }

// Rule 4.5: OSL(n) - One-Shot Layer
osl_action = { ^"OSL" ~ "(" ~ layer_reference ~ ")" }

// Rule 4.7: TT(n) - Layer Activate or Tap Toggle
tt_action = { ^"TT" ~ "(" ~ layer_reference ~ ")" }

// Rule 4.8: TG(n) - Layer Toggle
tg_action = { ^"TG" ~ "(" ~ layer_reference ~ ")" }

// Rule 4.9: TO(n) - Layer Toggle Only
to_action = { ^"TO" ~ "(" ~ layer_reference ~ ")" }

// Grouping for Layer Actions
layer_action = _{
    df_action | mo_action | lm_action | lt_action |
    osl_action | tt_action | tg_action | to_action
}

// Rule 5: MT(key, modifier) - Modifier Tap-Hold
mt_action = { ^"MT" ~ "(" ~ keycode_name ~ "," ~ modifier_combination ~ ")" }

// Rule 6: TH(key-tap, key-hold) - Generic Tap-Hold
th_action = { ^"TH" ~ "(" ~ keycode_name ~ "," ~ keycode_name ~ ")" }

// Grouping for Tap/Hold Actions
tap_hold_action = _{ mt_action | th_action }

// Rule 7: SHIFTED(key)
shifted_action = { ^"SHIFTED" ~ "(" ~ keycode_name ~ ")" }

// --- Top Level Rules ---

// A single key action entry in the map
// Order is important: more specific function-like rules first, then aliases/specials, then simple keycodes.
key_action = _{ // Consume surrounding whitespace/comments implicitly
    wm_action | osm_action | layer_action | tap_hold_action | shifted_action | no_action | transparent_action | simple_keycode
}

// The entire key map string: Start, zero or more key actions, End.
key_map = { SOI ~ key_action* ~ EOI }

// ============================================================================
// rules for matrix_map parsing

// Define the coordinate structure, capturing row and col numbers
// Make the rule itself non-silent ({}) so we get pairs for it
coordinate = { "(" ~ number ~ "," ~ number ~ ")" }

// The main rule: Start, zero or more coordinates or whitespace occurrences, End.
// This ensures the entire string consists *only* of valid coordinates and whitespace.
matrix_map = { SOI ~ (coordinate | WHITESPACE)* ~ EOI }