modules: cyclic import detection

compiler/modules.v

@@ -0,0 +1,141 @@
+// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+
+module main
+
+struct ModDepGraphNode  {
+	name string
+	deps []string
+}
+
+struct ModDepGraph {
+pub:
+	mut:
+	acyclic bool
+	nodes   []ModDepGraphNode
+}
+
+struct DepSet {
+	mut: 
+	items []string
+}
+
+pub fn(mapset mut DepSet) add(item string) {
+	mapset.items << item
+}
+
+pub fn(mapset &DepSet) diff(otherset DepSet) DepSet {
+	mut diff := DepSet{}
+	for item in mapset.items {
+		if !item in otherset.items {
+			diff.items << item
+		}
+	}
+	return diff
+}
+
+pub fn(mapset &DepSet) size() int {
+	return mapset.items.len
+}
+
+pub fn new_mod_dep_graph() *ModDepGraph {
+	return &ModDepGraph{
+		acyclic: true
+	}
+}
+
+pub fn(graph mut ModDepGraph) from_import_tables(import_tables []FileImportTable) {
+	for fit in import_tables {
+		mut deps := []string
+		for _, m in fit.imports {
+			deps << m
+		}
+		graph.add(fit.module_name, deps)
+	}
+}
+
+pub fn(graph mut ModDepGraph) add(mod string, deps []string) {
+	graph.nodes << ModDepGraphNode{
+		name: mod,
+		deps: deps
+	}
+}
+
+pub fn(graph &ModDepGraph) resolve() *ModDepGraph {
+	mut node_names := map[string]ModDepGraphNode{}
+	mut node_deps := map[string]DepSet{}
+
+	for _, node in graph.nodes {
+		node_names[node.name] = node
+
+		mut dep_set := DepSet{}
+		for _, dep in node.deps {
+			dep_set.add(dep)
+		}
+		node_deps[node.name] = dep_set
+	}
+
+	mut resolved := new_mod_dep_graph()
+	for node_deps.size != 0 {
+		mut ready_set := DepSet{}
+		for name, deps in node_deps {
+			if deps.size() == 0 {
+				ready_set.add(name)
+			}
+		}
+
+		if ready_set.size() == 0 {
+			mut g := new_mod_dep_graph()
+			g.acyclic = false
+			for name, _ in node_deps {				
+				g.nodes << node_names[name]
+			}
+			return g
+		}
+
+		ready_set.items.len > 0 {
+			mut new_set := map[string]DepSet{}
+			for name in ready_set.items {
+				// node_deps.remove(name)
+				resolved.nodes << node_names[name]
+			}
+			// remove once we have map.remove/delete 
+			for k, d in node_deps {
+				if !k in ready_set.items {
+					new_set[k] = d
+				}
+			}
+			node_deps = new_set
+		}
+
+		for name, deps in node_deps {
+			node_deps[name] = deps.diff(ready_set)
+		}
+	}
+
+	return resolved
+}
+
+pub fn(graph &ModDepGraph) imports() []string {
+	mut mods := []string
+	for node in graph.nodes {
+		if node.name == 'main' {
+			continue
+		}
+		mods << node.name
+	}
+	return mods
+}
+
+pub fn(graph &ModDepGraph) last_node() {
+	return graph.nodes[graph.nodes.len-1]
+}
+
+pub fn(graph &ModDepGraph) display() {
+	for _, node in graph.nodes {
+		for _, dep in node.deps {
+			println(' * $node.name -> $dep')
+		}
+	}
+}