# Make sure to configure this script!
# 1. Change `TEAM_LINEAR` properties below to match your Linear team
# 2. Optionally add more teams
# 3. Change the value of `DEPLOYED_TO_STAGING_GIT_TAG` to the tag/branch you use for deploys to staging
# 4. Change the value of `DEPLOYED_TO_PRODUCTION_GIT_TAG` to the tag/branch you use for deploys to production
#
# Usage:
#   LINEAR_API_KEY=... GITHUB_API_KEY=... ruby move_deployed_linear_issues.rb
#
# Adding new teams (change "LinearTeam" to your team name):
# - fetch your team ID with this Graphql query:
# query Teams {
#   teams(filter: {name: {eq: "LinearTeam"}}) {
#     nodes {
#       id
#       name
#     }
#   }
# }
# - fetch your workflow state ids with this Graphql query:
# query WorkflowStates {
#   workflowStates(filter: {team: {name: {eq: "LinearTeam"}}}) {
#     nodes {
#       id
#       name
#       team {
#         name
#       }
#     }
#   }
# }
# - add your team to TEAMS below
require "json"
require "uri"
require "net/http"

class GraphqlClient
  def initialize(endpoint:, key:)
    @uri = URI.parse(endpoint)
    @key = key
    @http = Net::HTTP.new(@uri.host, @uri.port)
  end

  def query(query)
    response = Net::HTTP.start(@uri.host, @uri.port, use_ssl: @uri.scheme == 'https') do |http|
      request = Net::HTTP::Post.new(
        @uri.request_uri,
        "Content-Type" => "application/json",
        "Authorization" => "Bearer #{@key}",
      )
      request.body = {query: query}.to_json
      http.request(request)
    end

    unless response.code.to_i == 200
      raise "Got bad status code when requesting #{@uri}: #{response.code}"
    end

    json = JSON.parse(response.body)
    if json.key?("errors")
      raise "Got error on Graphql query: #{json}"
    end

    json
  end
end

PullRequest = Struct.new(:repo_name, :number, keyword_init: true)

CommitDeployStatus = Struct.new(:staging, :production, keyword_init: true)
class CommitDeployStatus
  def deployed?
    staging || production
  end
end

LinearIssue = Struct.new(:id, :number, :title, :state, :pull_requests, keyword_init: true)

LinearState = Struct.new(:id, :name, keyword_init: true)

Team = Struct.new(:id, :name, :merged_state, :staging_state, :production_state, keyword_init: true)

TEAM_LINEAR = Team.new(
  id: "some team id",
  name: "some team name",
  merged_state: LinearState.new(
    id: "the id of the merged state column",
    name: "the name of the merged state column",
  ),
  # this one can be nil if your team doesn't have a staging column
  staging_state: LinearState.new(
    id: "the id of the 'staging' state column",
    name: "the name of the 'staging' state column",
  ),
  production_state: LinearState.new(
    id: "the id of the 'production' state column",
    name: "the name of the 'production' state column",
  ),
)

TEAMS = [
  TEAM_LINEAR,
].freeze

DEPLOYED_TO_STAGING_GIT_TAG = "origin/the-tag-you-use-for-deploys-to-staging"
DEPLOYED_TO_PRODUCTION_GIT_TAG = "origin/the-tag-you-use-for-deploys-to-production"

class LinearWorkflowChanger
  attr_reader :linear
  attr_reader :github

  def initialize
    @linear = GraphqlClient.new(
      endpoint: "https://api.linear.app/graphql".freeze,
      key: ENV.fetch("LINEAR_API_KEY"),
    )

    @github = GraphqlClient.new(
      endpoint: "https://api.github.com/graphql".freeze,
      key: ENV.fetch("GITHUB_API_KEY"),
    )
  end

  def do_it
    `git fetch`

    TEAMS.each do |team|
      puts "Processing Team #{team.name} Linear issues..."
      do_it_for_team(team)
    end
  end

  def do_it_for_team(team)
    linear_merged_or_staging_issues(team).each do |issue|
      process_team_issue(team, issue)
    end
  end

  def linear_merged_or_staging_issues(team)
    state_names =
      [team.merged_state, team.staging_state]
        .compact
        .map(&:name)

    fetch_linear_issues(%(
      query Team {
        team(id: "#{team.id}") {
          issues(filter: {
            state: {
              name: {
                in: #{state_names}
              }
            }
          }) {
            nodes {
              id
              number
              title
              state {
                name
              }
              integrationResources {
                nodes {
                  pullRequest {
                    repoName
                    number
                  }
                }
              }
            }
          }
        }
      }
    ))
  end

  def process_team_issue(team, issue)
    return if issue.pull_requests.empty?

    oids = issue.pull_requests.map { |pr|
      fetch_github_pr_merge_commit_oid(pr)
    }

    # Bail out unless all PRs have been merged
    return unless oids.all?

    deploy_statuses = oids.map { |oid|
      commit_deploy_status(oid)
    }

    # If all PRs are in production, move the issue to "Done/Deployed"
    if deploy_statuses.all?(&:production)
      set_linear_issue_state(issue, team.production_state)
      return
    end

    staging_state = team.staging_state

    # Not all teams have a column for "In Staging"
    return unless staging_state

    # If the issue in staging already, it won't move anywhere else for now
    return if issue.state == staging_state.name

    # There's also nothing else to do unless all PRs are in staging
    return unless deploy_statuses.all?(&:staging)

    set_linear_issue_state(issue, staging_state)
  end

  def fetch_linear_issues(query)
    linear
      .query(query)
      .dig("data", "team", "issues", "nodes")
      .map do |issue|
        LinearIssue.new(
          id: issue.fetch("id"),
          number: issue.fetch("number"),
          title: issue.fetch("title"),
          state: issue.dig("state", "name"),
          pull_requests: issue.dig("integrationResources", "nodes").map do |pr|
            PullRequest.new(
              repo_name: pr.dig("pullRequest", "repoName"),
              number: pr.dig("pullRequest", "number"),
            )
          end,
        )
      end
  end

  def fetch_github_pr_merge_commit_oid(pull_request)
    # Fetch the PR's merge commit from GitHub
    github
      .query(%(
        query GitHub {
          repository(owner: "NoRedInk", name: "#{pull_request.repo_name}") {
            pullRequest(number: #{pull_request.number}) {
              mergeCommit {
                oid
              }
            }
          }
        }
      ))
      .dig("data", "repository", "pullRequest", "mergeCommit", "oid")
  end

  def commit_deploy_status(commit_oid)
    # Check in which remote branches this commit is included.
    branches = `git branch --contains #{commit_oid} --format='%(refname:short)' -a -r`.split(/\n+/)
    CommitDeployStatus.new(
      staging: branches.include?(DEPLOYED_TO_STAGING_GIT_TAG),
      production: branches.include?(DEPLOYED_TO_PRODUCTION_GIT_TAG),
    )
  end

  def set_linear_issue_state(issue, state)
    update_linear_issue(issue.id, "stateId", %("#{state.id}"))

    puts "- Moved issue ##{issue.number} (#{issue.title}) from '#{issue.state}' to '#{state.name}'"
  end

  def update_linear_issue(issue_id, key, value)
    linear.query(%(
      mutation IssueUpdate {
        issueUpdate(
          id: "#{issue_id}",
          input: {
            #{key}: #{value}
          }
        ) {
          success
        }
      }
    ))
  end
end

LinearWorkflowChanger.new.do_it