module Rigor::ModuleGraph::Mermaid

# File lib/rigor/module_graph/mermaid.rb, line 109
def assign_node_ids(edges)
  names = edges.flat_map { |edge| [edge.from, edge.to] }.uniq.sort
  names.each_with_index.to_h { |name, idx| [name, "n#{idx}"] }
end

# File lib/rigor/module_graph/mermaid.rb, line 91
def better_tag?(candidate, current)
  return false if current == "unresolved"
  return true if candidate == "unresolved"

  (KIND_PRIORITY[candidate] || 99) < (KIND_PRIORITY[current] || 99)
end

# File lib/rigor/module_graph/mermaid.rb, line 114
def build_groups(names, collapse, groups)
  if groups && !groups.empty?
    clusters = Hash.new { |h, k| h[k] = [] }
    ungrouped = []
    names.each do |name|
      if (label = groups[name])
        clusters[label] << name
      else
        ungrouped << name
      end
    end
    [clusters, ungrouped]
  else
    group_by_prefix(names, collapse)
  end
end

# File lib/rigor/module_graph/mermaid.rb, line 162
def cluster_id(prefix)
  "sg_#{prefix.gsub(/[^A-Za-z0-9_]+/, "_")}"
end

# File lib/rigor/module_graph/mermaid.rb, line 98
def dedup(edges)
  seen = {}
  edges.each_with_object([]) do |edge, acc|
    key = edge.dedup_key
    next if seen[key]

    seen[key] = true
    acc << edge
  end
end

# File lib/rigor/module_graph/mermaid.rb, line 166
def escape_label(name)
  name.gsub('"', "#quot;")
end

# File lib/rigor/module_graph/mermaid.rb, line 131
def group_by_prefix(names, collapse)
  prefixes = Array(collapse).map(&:to_s).reject(&:empty?)
  return [{}, names] if prefixes.empty?

  sorted = prefixes.sort_by { |p| -p.length }
  clusters = Hash.new { |h, k| h[k] = [] }
  ungrouped = []
  names.each do |name|
    match = sorted.find { |p| name.start_with?(p + "::") }
    if match
      clusters[match] << name
    else
      ungrouped << name
    end
  end
  [clusters, ungrouped]
end

# File lib/rigor/module_graph/mermaid.rb, line 41
def render(edges, collapse: [], groups: nil)
  edges = dedup(edges)
  node_ids = assign_node_ids(edges)
  clusters, ungrouped = build_groups(node_ids.keys.sort, collapse, groups)

  out = +"flowchart LR\n"
  clusters.each do |label, members|
    out << render_cluster(label, members, node_ids, use_namespace_prefix: groups.nil?)
  end
  ungrouped.each do |name|
    out << "  #{node_ids[name]}[\"#{escape_label(name)}\"]\n"
  end
  out << "\n" unless node_ids.empty?
  edges.each do |edge|
    arrow = ARROW_FOR_KIND.fetch(edge.kind, "-->")
    out << "  #{node_ids[edge.from]} #{arrow}|#{edge.kind}| #{node_ids[edge.to]}\n"
  end
  out << "\n"
  out << CLASS_DEFS
  # One class assignment per node id. Mermaid silently keeps
  # the last assignment but starts to error out when the same
  # `class N kind;` line repeats many hundreds of times in a
  # large graph, so we dedupe and pick the most structural
  # kind per node (inherits > include > prepend > extend >
  # const_ref) so the resulting colour conveys intent.
  out << render_class_assignments(edges, node_ids)
  out
end

# File lib/rigor/module_graph/mermaid.rb, line 78
def render_class_assignments(edges, node_ids)
  per_node = {}
  edges.each do |edge|
    id = node_ids[edge.to]
    tag = edge.confidence == "unresolved" ? "unresolved" : edge.kind
    current = per_node[id]
    if current.nil? || better_tag?(tag, current)
      per_node[id] = tag
    end
  end
  per_node.map { |id, tag| "  class #{id} #{tag};\n" }.join
end

# File lib/rigor/module_graph/mermaid.rb, line 149
def render_cluster(label, members, node_ids, use_namespace_prefix: true)
  out = +"  subgraph #{cluster_id(label)} [\"#{escape_label(label)}\"]\n"
  members.each do |name|
    short = use_namespace_prefix ? name.sub(/\A#{Regexp.escape(label)}::/, "") : name
    out << "    #{node_ids[name]}[\"#{escape_label(short)}\"]\n"
  end
  out << "  end\n"
end