better (require) implementation

Close #16

6 files changed, 166 insertions, 107 deletions

diff --git a/alv/builtin.moon b/alv/builtin.moon
index 9b88bd4..022c40c 100644
--- a/alv/builtin.moon
+++ b/alv/builtin.moon
@@ -13,7 +13,6 @@ import Cell from require 'alv.cell'
 import Scope from require 'alv.scope'
 import Tag from require 'alv.tag'
 import op_invoke from require 'alv.invoke'
-import load from require 'alv.cycle'
 lfs = require 'lfs'
 
 doc = ValueStream.meta
@@ -85,16 +84,6 @@ All arguments have to be evaltime constant."
 
       Result!
 
-load_module = (name, tag) ->
-  Error.wrap "loading module '#{name}'", ->
-    ok, lua = pcall require, "alv-lib.#{name}"
-    if ok
-      ValueStream.wrap lua
-    else
-      result,_ = load.loadfile "#{name}.alv"
-      assert result, "empty return value"
-      result.value
-
 require_ = ValueStream.meta
   meta:
     name: 'require'
@@ -111,7 +100,7 @@ require_ = ValueStream.meta
       name = result\const!\unwrap 'str'
 
       L\trace @, "loading module #{name}"
-      Result value: load_module name, @tag
+      COPILOT\require name
 
 import_ = ValueStream.meta
   meta:
@@ -127,10 +116,11 @@ current scope."
       L\trace "evaling #{@}"
       assert #tail > 0, "'import' requires at least one arguments"
 
-      for i, child in ipairs tail
+      children = for i, child in ipairs tail
         name = child\quote(scope)\unwrap 'sym'
-        scope\set name, Result value: load_module name, @tag\clone Tag i
-      Result!
+        with COPILOT\require name
+          scope\set name, \make_ref!
+      Result :children
 
 import_star = ValueStream.meta
   meta:
@@ -145,11 +135,10 @@ Requires modules `sym1`, `sym2`, … and merges them into the current scope."
       L\trace "evaling #{@}"
       assert #tail > 0, "'import' requires at least one arguments"
 
-      for i, child in ipairs tail
-        value = load_module child\quote(scope)\unwrap('sym'), @tag\clone Tag i
-        scope\use value\unwrap 'scope'
-
-      Result!
+      children = for i, child in ipairs tail
+        with COPILOT\require child\quote(scope)\unwrap 'sym'
+          scope\use .value\unwrap 'scope'
+      Result :children
 
 export_ = ValueStream.meta
   meta:
diff --git a/alv/copilot.moon b/alv/copilot.moon
index d4612c8..5d9536a 100644
--- a/alv/copilot.moon
+++ b/alv/copilot.moon
@@ -4,14 +4,10 @@
 -- @classmod Copilot
 lfs = require 'lfs'
 import Scope from require 'alv.scope'
-import Registry from require 'alv.registry'
+import Module from require 'alv.module'
 import Error from require 'alv.error'
-import loadfile from require 'alv.load'
-
-spit = (file, str) ->
-  file = io.open file, 'w'
-  file\write str
-  file\close!
+import Result from require 'alv.result'
+import ValueStream from require 'alv.stream'
 
 export COPILOT
 
@@ -24,7 +20,7 @@ class Copilot
   -- @tparam string file name/path of the alive file to watch and execute
   new: (file) =>
     @T = 0
-    @registry = Registry!
+    @last_modules = {}
     @open file if file
 
 --- members
@@ -36,27 +32,44 @@ class Copilot
   --- change the running script.
   -- @tparam string file
   open: (file) =>
-    mode = lfs.attributes file, 'mode'
-    if mode != 'file'
-      error "not a file: #{file}"
-
-    @last_modification = 0
-    @file = file
+    if old = @last_modules.__root
+      old\destroy!
+
+    @last_modules.__root = Module file
+
+  --- require a module.
+  -- @tparam string name
+  -- @treturn Result result
+  require: (name) =>
+    Error.wrap "loading module '#{name}'", ->
+      ok, lua = pcall require, "alv-lib.#{name}"
+      if ok
+        Result value: ValueStream.wrap lua
+      else
+        assert @modules, "no current eval cycle?"
+        if mod = @modules[name]
+          mod.root\make_ref!
+        else
+          @modules[name] = @last_modules[name] or Module "#{name}.alv"
+          @modules[name]\eval!
+          @modules[name].root
 
   --- poll for changes and tick.
   tick: =>
     assert not COPILOT, "another Copilot is already running!"
+    return unless @last_modules.__root
+
     COPILOT = @
     @T += 1
 
-    return unless @file
     @poll!
 
-    if @root
+    root = @last_modules.__root
+    if root and root.root
       L\set_time 'run'
       ok, error = Error.try "updating", ->
-        @root\tick_io!
-        @root\tick!
+        root.root\tick_io!
+        root.root\tick!
       if not ok
         L\print error
 
@@ -67,28 +80,34 @@ class Copilot
   -- Call `eval` if there are any, and write changed and newly added modules
   -- back to disk.
   poll: =>
-    { :mode, :modification } = (lfs.attributes @file) or {}
-    if mode != 'file'
-      return
+    dirty = {}
+    for name, mod in pairs @last_modules
+      if mod\poll!
+        table.insert dirty, mod
 
-    if @last_modification < modification
-      L\set_time 'eval'
-      L\log "#{@file} changed at #{modification}"
-      @eval!
-      @last_modification = os.time!
+    return if #dirty == 0
+
+    L\set_time 'eval'
+    L\print "changed to files: #{table.concat [m.file for m in *dirty], ', '}"
+
+    @modules = { __root: @last_modules.__root }
+    ok, err = Error.try "processing changes", @modules.__root\eval
 
-  --- perform an eval-cycle.
-  eval: =>
-    @registry\begin_eval!
-    ok, root, ast = Error.try "running '#{@file}'", loadfile, @file
     if not ok
-      L\print root
-      @registry\rollback_eval!
+      for name, mod in pairs @modules
+        mod\rollback!
+      @modules = {}
+      L\error err
       return
 
-    @registry\end_eval!
-    @root = root
-    spit @file, ast\stringify!
+    for name, mod in pairs @last_modules
+      if not @modules[name]
+        mod\destroy!
+
+    for name, mod in pairs @modules
+      mod\finish!
+
+    @last_modules, @modules = @modules, nil
 
 {
   :Copilot
diff --git a/alv/load.moon b/alv/load.moon
deleted file mode 100644
index 2ae2a9b..0000000
--- a/alv/load.moon
+++ /dev/null
@@ -1,43 +0,0 @@
-----
--- Functions for loading strings and files of alive code.
---
--- @module load
-import Result from require 'alv.result'
-import Builtin from require 'alv.base'
-import Scope from require 'alv.scope'
-import Error from require 'alv.error'
-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!
-
---- Attempt to load alive code from string.
---
--- @tparam string code the code to load
--- @tparam ?string file name of the source file (for error reporting)
--- @treturn Result
--- @treturn AST the parsed and updated AST
-loadstring = (code, file='(unnamed)') ->
-  Error.wrap "evaluating '#{file}'", ->
-    ast = program\match code
-    if not ast
-      error Error 'syntax', "failed to parse"
-
-    scope = Scope builtin
-    result = ast\eval scope
-    result, ast
-
---- Attempt to load alive code from a file.
---
--- @tparam string file filepath of the source file
--- @treturn Result
--- @treturn AST the parsed and updated AST
-loadfile = (file) -> loadstring (slurp file), file
-
-{
-  :loadstring
-  :loadfile
-}
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
+}
diff --git a/alv/registry.moon b/alv/registry.moon
index 4bd03f6..ba35a18 100644
--- a/alv/registry.moon
+++ b/alv/registry.moon
@@ -45,12 +45,23 @@ class Registry
   -- `end_eval` or `rollback_eval`.
   begin_eval: =>
     @grab!
+    assert not @map, "unfinished evaluation cycle"
     @map, @pending = {}, {}
 
+  --- abort an evaluation cycle.
+  --
+  -- Unset the active Registry.
+  rollback_eval: =>
+    for { :tag, :expr } in *@pending
+      expr\destroy!
+
+    @map, @pending = nil, nil
+
   --- end an evaluation cycle.
   --
   -- Register all pending `Tag`s and destroy all orphaned registrations.
   -- Unset the active Registry.
+  -- @treturn bool whether any changes to the AST were made
   end_eval: =>
     for tag, val in pairs @last_map
       val\destroy! unless @map[tag]
@@ -65,14 +76,10 @@ class Registry
       tag\set next_tag
       @map[tag\index!] = expr
 
-    @last_map = @map
-    @release!
+    dirty = #@pending > 0
+    @last_map, @map, @pending = @map, nil, nil
 
-  --- abort an evaluation cycle.
-  --
-  -- Unset the active Registry.
-  rollback_eval: =>
-    @release!
+    dirty
 
   --- set the active Registry.
   grab: =>
@@ -84,13 +91,22 @@ class Registry
     assert @ == Registry.active_registry, "not the active registry!"
     Registry.active_registry, @prev = @prev, nil
 
+  --- destroy this Registry and all associated Registrations.
+  -- needs to be called *after* `:eval`.
+  destroy: =>
+    assert not @tag, "unfinished evaluation cycle"
+    for tag, val in pairs @last_map
+      val\destroy!
+
+    @last_map = {}
+
 --- static functions
 -- @section static
 
   --- create a new Registry.
   -- @classmethod
   new: =>
-    @last_map, @map = {}, {}
+    @last_map = {}
 
   --- get the active Registry.
   --
diff --git a/dist/rocks/alive-scm-3.rockspec b/dist/rocks/alive-scm-3.rockspec
index 7c9cbf0..4623319 100644
--- a/dist/rocks/alive-scm-3.rockspec
+++ b/dist/rocks/alive-scm-3.rockspec
@@ -47,8 +47,8 @@ build = {
       ["alv.error"] = "alv/error.moon",
       ["alv.init"] = "alv/init.moon",
       ["alv.invoke"] = "alv/invoke.moon",
-      ["alv.load"] = "alv/load.moon",
       ["alv.logger"] = "alv/logger.moon",
+      ["alv.module"] = "alv/module.moon",
       ["alv.parsing"] = "alv/parsing.moon",
       ["alv.registry"] = "alv/registry.moon",
       ["alv.result"] = "alv/result.moon",