[App::Pls] implemented 'fetch'

All t/subcommands/fetch.t tests now pass.

lib/App/Pls.pm

@@ -1,15 +1,44 @@
 use v6;
 
-enum State <gone fetched built tested installed>;
+subset State of Str where {
+    'gone' | 'fetched' | 'built' | 'tested' | 'installed'
+};
 enum Result <failure success forced-success>;
 
 role App::Pls::ProjectsState {
+    method state-of($project --> State) { !!! }
+    method set-state-of($project, State $state) { !!! }
+    method deps-of($project) { !!! }
 }
 
 class App::Pls::ProjectsState::Hash does App::Pls::ProjectsState {
+    has %!projects;
+
+    method new(%projects is rw) {
+        self.bless(*, :%projects);
+    }
+
+    method state-of($project --> State) {
+        (%!projects{$project} // { :state<gone> })<state> // 'gone';
+    }
+
+    method set-state-of($project, State $state) {
+        %!projects{$project}<state> = $state;
+    }
+
+    method deps-of($project) {
+        if %!projects.exists($project) {
+            if %!projects{$project}.exists('deps') {
+                return %!projects{$project}<deps>.list;
+            }
+            return ();
+        }
+        die "No such project: $project";
+    }
 }
 
 role App::Pls::Fetcher {
+    method fetch($project) { !!! }
 }
 
 role App::Pls::Builder {
@@ -27,11 +56,33 @@ class App::Pls::Core {
     has App::Pls::Builder       $!builder;
 
     method state-of($project) {
-        return -1;
+        return $!projects.state-of($project);
     }
 
-    method fetch(*@projects) {
-        return;
+    method fetch(*@projects --> Result) {
+        for @projects -> $project {
+            my %*seen-projects;
+            return failure
+                if self!fetch-helper($project) == failure;
+        }
+        return success;
+    }
+
+    method !fetch-helper($project --> Result) {
+        %*seen-projects{$project}++;
+        for $!projects.deps-of($project) -> $dep {
+            return failure
+                if %*seen-projects{$dep};
+            return failure
+                if self!fetch-helper($dep) == failure;
+        }
+        if $!fetcher.fetch($project) == success {
+            $!projects.set-state-of($project, 'fetched');
+            return success;
+        }
+        else {
+            return failure;
+        }
     }
 
     method build(*@projects) {

t/subcommands/fetch.t

@@ -19,6 +19,9 @@ my %projects =
 ;
 
 class Mock::Fetcher does App::Pls::Fetcher {
+    method fetch($project --> Result) {
+        $project eq 'will-fail' ?? failure !! success;
+    }
 }
 
 my $core = App::Pls::Core.new(