better (require) implementation

Close #16

1 files changed, 78 insertions, 0 deletions

diff --git a/alv/module.moon b/alv/module.moon
new file mode 100644
index 0000000..b6244d8
--- /dev/null
+++ b/alv/module.moon
@@ -0,0 +1,78 @@
+----
+-- Per-file execution context.
+--
+-- @classmod Module
+import Registry from require 'alv.registry'
+import Error from require 'alv.error'
+import Scope from require 'alv.scope'
+import program from require 'alv.parsing'
+builtin = require 'alv.builtin'
+
+slurp = (file) ->
+  file = assert (io.open file, 'r'), Error 'io', "couldn't open '#{file}'"
+  with file\read '*all'
+    file\close!
+
+spit = (file, str) ->
+  file = io.open file, 'w'
+  file\write str
+  file\close!
+
+class Module
+--- static functions
+-- @section static
+
+  --- create a new Module.
+  -- @classmethod
+  new: (@file) =>
+    @registry = Registry!
+    @last_modification = 0
+
+--- members
+-- @section members
+
+  --- check whether file was changed.
+  -- @treturn bool whether the file was changed since the last call
+  poll: =>
+    { :mode, :modification } = (lfs.attributes @file) or {}
+    assert mode == 'file', Error 'io', "not a file: '#{file}'"
+
+    if @last_modification < modification
+      true
+
+  --- start an evaluation cycle.
+  --
+  -- If the module has already been evaluated this tick, this is a noop.
+  -- Otherwise, register the module with the `Copilot`. Updates `root`.
+  eval: =>
+    @last_modification = os.time!
+    @ast = Error.wrap "parsing '#{@file}'", -> program\match slurp @file
+    assert @ast, Error 'syntax', "failed to parse"
+
+    scope = Scope builtin
+    @registry\begin_eval!
+    @root = Error.wrap "evaluating '#{@file}'", @ast\eval, scope, @registry
+    @registry\release!
+
+  --- rollback the last evaluation cycle.
+  rollback: => @registry\rollback_eval!
+
+  --- finish the last evaluation cycle.
+  finish: =>
+    tags_changed = @registry\end_eval!
+    if tags_changed
+      spit @file, @ast\stringify!
+
+  --- destroy this module.
+  destroy: =>
+    @registry\destroy!
+
+  --- the last updated AST tree for this module.
+  -- @tfield ?AST ast
+
+  --- the root Result of this module.
+  -- @tfield ?Result root
+
+{
+  :Module
+}