feat: add SubjectGraphComponent and graph controllers

- SubjectGraphComponent builds nodes (with availability/completion
  status), edges (from prerequisite trees), and semester labels
- Planner::GraphsController shows planned subjects grouped by
  user-defined semesters
- Subjects::GraphsController shows curriculum subjects filtered
  by category
- Add routes: planner/graph and subjects/graph

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: RenzoMinelli

app/components/subject_graph_component.html.erb

@@ -0,0 +1,7 @@
+<div
+  data-controller="subject-graph"
+  data-subject-graph-nodes-value="<%= nodes.to_json %>"
+  data-subject-graph-edges-value="<%= edges.to_json %>"
+  data-subject-graph-semester-labels-value="<%= semester_labels.to_json %>"
+  class="subject-graph-container border border-gray-200 rounded-lg w-[100vw] relative left-[50%] -translate-x-1/2 flex-1 min-h-0 overflow-hidden">
+</div>

app/components/subject_graph_component.rb

@@ -0,0 +1,81 @@
+class SubjectGraphComponent < ViewComponent::Base
+  def initialize(subjects:, current_student:, semester_map: nil)
+    @subjects = subjects
+    @current_student = current_student
+    @semester_map = semester_map
+  end
+
+  def nodes
+    @subjects.map do |subject|
+      {
+        id: subject.id,
+        code: subject.code,
+        name: subject.short_name || subject.name,
+        url: helpers.subject_path(subject),
+        available: @current_student.available?(subject),
+        completed: @current_student.approved?(subject),
+        semester: semester_for(subject)
+      }
+    end
+  end
+
+  def edges
+    subject_ids = Set.new(@subjects.map(&:id))
+    edges = []
+
+    @subjects.each do |subject|
+      collect_prerequisite_edges(subject.course&.prerequisite_tree, subject.id, subject_ids, edges)
+    end
+
+    edges.uniq
+  end
+
+  def semester_labels
+    semesters = @subjects.map { |s| semester_for(s) }.uniq.sort
+
+    semesters.index_with do |sem|
+      semester_display_label(sem)
+    end
+  end
+
+  private
+
+  def semester_for(subject)
+    if @semester_map
+      @semester_map[subject.id] || 0
+    else
+      index = Subject::CATEGORIES.index(subject.category&.to_sym)
+      index ? index + 1 : 0
+    end
+  end
+
+  def semester_display_label(semester)
+    return "Otras" if semester == 0
+
+    if @semester_map
+      "Semestre #{semester}"
+    else
+      category = Subject::CATEGORIES[semester - 1]
+      category ? helpers.formatted_category(category.to_s) : "Semestre #{semester}"
+    end
+  end
+
+  def collect_prerequisite_edges(prerequisite, target_subject_id, subject_ids, edges)
+    return unless prerequisite
+
+    case prerequisite
+    when SubjectPrerequisite
+      source_subject_id = prerequisite.approvable_needed.subject_id
+      if subject_ids.include?(source_subject_id)
+        edges << { source: source_subject_id, target: target_subject_id }
+      end
+    when LogicalPrerequisite
+      # Skip "not" operators - they represent inverse relationships
+      return if prerequisite.logical_operator == "not"
+
+      prerequisite.operands_prerequisites.each do |child|
+        collect_prerequisite_edges(child, target_subject_id, subject_ids, edges)
+      end
+    end
+  end
+end

app/controllers/planner/graphs_controller.rb

@@ -0,0 +1,17 @@
+module Planner
+  class GraphsController < ApplicationController
+    before_action :authenticate_user!
+
+    def show
+      subject_plans = current_user.subject_plans
+                                  .includes(subject: [:course, :exam])
+
+      @semester_map = subject_plans.to_h do |subject_plan|
+        [subject_plan.subject_id, subject_plan.semester]
+      end
+
+      @subjects = subject_plans.map(&:subject)
+      TreePreloader.preload(@subjects)
+    end
+  end
+end

app/controllers/subjects/graphs_controller.rb

@@ -0,0 +1,13 @@
+module Subjects
+  class GraphsController < ApplicationController
+    def show
+      categories = params[:categories] || []
+
+      @subjects = current_degree_plan.subjects
+                                     .where(category: categories)
+                                     .includes(:course, :exam)
+
+      TreePreloader.preload(@subjects)
+    end
+  end
+end

config/routes.rb

@@ -42,6 +42,11 @@
 
     namespace :planner do
       resources :not_planned_subjects, only: :index
+      resource :graph, only: :show
+    end
+
+    namespace :subjects do
+      resource :graph, only: :show
     end
 
     resource :user_onboardings, only: :update