# Copyright (C) 2012-2026 Zammad Foundation, https://zammad-foundation.org/

class GitHub
  class LinkedIssue

    STATES_MAPPING = {
      'OPEN'   => 'open',
      'CLOSED' => 'closed'
    }.freeze

    QUERY = <<-GRAPHQL.freeze
      query($repositor_owner: String!, $repository_name: String!, $issue_id: Int!) {
       repository(owner: $repositor_owner, name: $repository_name) {
         issue(number: $issue_id) {
           number
           title
           state
           url
           milestone {
             title
           }
           assignees(last: 100) {
             edges {
               node {
                 name
               }
             }
           }
           labels(last: 100) {
             edges {
               node {
                 name
                 color
               }
             }
           }
         }
       }
     }
    GRAPHQL

    attr_reader :client

    def initialize(client)
      @client = client
    end

    def find_by(url)
      @result = query_by_url(url)
      return if @result.blank?

      to_h
    end

    private

    def to_h
      {
        id:         @result['number'].to_s,
        title:      @result['title'],
        url:        @result['url'],
        icon_state: STATES_MAPPING.fetch(@result['state'], @result['state']),
        milestone:  milestone,
        assignees:  assignees,
        labels:     labels,
      }
    end

    def assignees
      @result['assignees']['edges'].map do |assignee|
        assignee['node']['name']
      end
    end

    def labels
      @result['labels']['edges'].map do |label|
        {
          text_color: text_color(label['node']['color']),
          color:      "##{label['node']['color']}",
          title:      label['node']['name']
        }
      end
    end

    def text_color(background_color)
      # Convert hex to RGB values.
      #  Supports only 6-digit hex color codes (e.g. RRGGBB).
      rgb_r = Integer("0x#{background_color[0..1]}") / 255.0
      rgb_g = Integer("0x#{background_color[2..3]}") / 255.0
      rgb_b = Integer("0x#{background_color[4..5]}") / 255.0

      # Calculate relative luminance (WCAG 2.0 formula).
      #   https://www.w3.org/TR/WCAG20/#contrast-ratiodef
      calc = proc { |rgb| rgb <= 0.03928 ? rgb / 12.92 : ((rgb + 0.055) / 1.055)**2.4 }
      relative_luminance = (0.2126 * calc.call(rgb_r)) + (0.7152 * calc.call(rgb_g)) + (0.0722 * calc.call(rgb_b))

      # Return the color with better contrast.
      #   https://stackoverflow.com/a/3943023
      relative_luminance > 0.179 ? '#000000' : '#FFFFFF'
    end

    def milestone
      @result.dig('milestone', 'title')
    end

    def query_by_url(url)
      response = client.perform(
        query:     GitHub::LinkedIssue::QUERY,
        variables: variables!(url)
      )

      response.dig('data', 'repository', 'issue')
    end

    def variables!(url)
      if url !~ %r{^https?://([^/]+)/([^/]+)/([^/]+)/issues/(\d+)$}
        raise Exceptions::UnprocessableContent, __('Invalid GitHub issue link format')
      end

      host            = $1
      repositor_owner = $2
      repository_name = $3
      id              = $4

      if client.endpoint.exclude?(host)
        raise Exceptions::UnprocessableContent, "Issue link doesn't match configured GitHub endpoint '#{client.endpoint}'"
      end

      {
        repositor_owner: repositor_owner,
        repository_name: repository_name,
        issue_id:        id.to_i,
      }
    end
  end
end