feat(parse_transition): first version of parse_transition, with tests

src/util/debug.moon

@@ -0,0 +1,24 @@
+---
+-- Recursively prints the contents of a table in a human-readable format.
+--
+-- This function traverses the provided table `tbl` and prints each key-value
+-- pair to the standard output. For nested tables, it calls itself recursively,
+-- increasing the indentation level to visually represent the table hierarchy.
+--
+-- @param tbl table: The table whose contents are to be printed.
+-- @param indent number: (Optional) The current indentation level. Defaults to 0.
+-- @return nil
+export print_table = (tbl, indent) ->
+  -- Use the “?=” operator to give a default value.
+  unless indent
+    indent = 0
+  -- Omit the extra “do” after the loop header.
+  for k, v in pairs tbl
+    formatting = string.rep("  ", indent) .. k .. ": "
+    if type(v) == "table"
+      print formatting
+      print_table v, indent + 1
+    elseif type(v) == "boolean"
+      print formatting .. tostring(v)
+    else
+      print formatting .. v

src/util/parse_transition.moon

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+require "src.util.string"
+require "src.util.validators"
+
+---
+-- parse_transition
+-- Parses a transition string into a table with:
+--   • target: the target state name,
+--   • type:   "after" | "every" | "on",
+--   • time:   number (if timer-based),
+--   • event:  string (if event-based).
+export parse_transition = (trans) ->
+  unless type(trans) == "string"
+    error "Transition must be a string"
+
+  words = split trans
+  unless #words == 3
+    error "Transition must consist of three words"
+
+  unless is_valid_symbol words[1]
+    error "Invalid state name"
+
+  switch words[2]
+    when "on"
+      unless is_valid_symbol words[3]
+        error "Invalid event name"
+      {target: words[1], event: words[3]}
+
+    when "after"
+      num = tonumber words[3]
+      unless is_valid_timer num
+        error "Invalid time value in 'after' transition type"
+      {target: words[1], after: num}
+
+    when "every"
+      num = tonumber words[3]
+      unless is_valid_timer num
+        error "Invalid time value in 'every' transition type"
+      {target: words[1], every: num}
+
+    else
+      error "Unknown transition type"

src/util/string.moon

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+---
+-- Splits the input string into an array of non-whitespace substrings.
+--
+-- This function uses Lua's pattern matching to iterate over the provided
+-- string `s` and collects each contiguous sequence of non-whitespace
+-- characters into a new table. If the input is not a string, the function
+-- raises an error.
+--
+-- @param s string: The string to be split. Must be a valid string.
+-- @return table: An array of substrings obtained by splitting `s` on whitespace.
+-- @raise error if the input parameter `s` is not a string.
+export split = (s) ->
+  unless type(s) == "string"
+    error "split() requires a string parameter"
+  chunks = {}
+  for substr in string.gmatch s, '%S+'
+    table.insert chunks, substr
+  chunks

src/util/validators.moon

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+---
+-- Determines if the provided timer value is valid.
+--
+-- A valid timer is defined as a number greater than zero.
+--
+-- @param x number: The timer value to validate.
+-- @return boolean: Returns `true` if `x` is a positive number; otherwise, returns `false` or `nil`.
+export is_valid_timer = (x) ->
+  x and x > 0
+
+---
+-- Checks whether the given string is a valid symbol.
+--
+-- A valid symbol is defined as a non-empty string that contains only
+-- alphabetic characters (A-Z and a-z). If the input is not a string,
+-- the function returns `false`.
+--
+-- @param s string: The string to be validated as a symbol.
+-- @return boolean: Returns `true` if `s` contains only letters; otherwise, returns `false`.
+export is_valid_symbol = (s) ->
+  -- Return false immediately if s is not a string.
+  unless type(s) == "string"
+    return false
+  -- Use Lua's pattern matching to ensure the string only contains letters.
+  if string.match s, "^[A-Za-z]+$"
+    true
+  else
+    false