# typed: true
# frozen_string_literal: true

require "tempfile"
require "utils/shell"
require "utils/formatter"

# A module that interfaces with GitHub, code like PAT scopes, credential handling and API errors.
module GitHub
  def self.pat_blurb(scopes = ALL_SCOPES)
    <<~EOS
      Create a GitHub personal access token:
      #{Formatter.url(
        "https://github.com/settings/tokens/new?scopes=#{scopes.join(",")}&description=Homebrew",
      )}
      #{Utils::Shell.set_variable_in_profile("HOMEBREW_GITHUB_API_TOKEN", "your_token_here")}
    EOS
  end

  API_URL = "https://api.github.com"
  API_MAX_PAGES = 50
  API_MAX_ITEMS = 5000

  CREATE_GIST_SCOPES = ["gist"].freeze
  CREATE_ISSUE_FORK_OR_PR_SCOPES = ["repo"].freeze
  CREATE_WORKFLOW_SCOPES = ["workflow"].freeze
  ALL_SCOPES = (CREATE_GIST_SCOPES + CREATE_ISSUE_FORK_OR_PR_SCOPES + CREATE_WORKFLOW_SCOPES).freeze
  GITHUB_PERSONAL_ACCESS_TOKEN_REGEX = /^(?:[a-f0-9]{40}|gh[po]_\w{36,251})$/.freeze

  # Helper functions to access the GitHub API.
  #
  # @api private
  module API
    extend T::Sig

    module_function

    # Generic API error.
    class Error < RuntimeError
      attr_reader :github_message
    end

    # Error when the requested URL is not found.
    class HTTPNotFoundError < Error
      def initialize(github_message)
        @github_message = github_message
        super
      end
    end

    # Error when the API rate limit is exceeded.
    class RateLimitExceededError < Error
      def initialize(reset, github_message)
        @github_message = github_message
        new_pat_message = ", or:\n#{GitHub.pat_blurb}" if API.credentials.blank?
        super <<~EOS
          GitHub API Error: #{github_message}
          Try again in #{pretty_ratelimit_reset(reset)}#{new_pat_message}
        EOS
      end

      def pretty_ratelimit_reset(reset)
        pretty_duration(Time.at(reset) - Time.now)
      end
    end

    # Error when authentication fails.
    class AuthenticationFailedError < Error
      def initialize(github_message)
        @github_message = github_message
        message = +"GitHub API Error: #{github_message}\n"
        message << if Homebrew::EnvConfig.github_api_token
          <<~EOS
            HOMEBREW_GITHUB_API_TOKEN may be invalid or expired; check:
              #{Formatter.url("https://github.com/settings/tokens")}
          EOS
        else
          <<~EOS
            The GitHub credentials in the macOS keychain may be invalid.
            Clear them with:
              printf "protocol=https\\nhost=github.com\\n" | git credential-osxkeychain erase
            #{GitHub.pat_blurb}
          EOS
        end
        super message.freeze
      end
    end

    # Error when the user has no GitHub API credentials set at all (macOS keychain or envvar).
    class MissingAuthenticationError < Error
      def initialize
        message = +"No GitHub credentials found in macOS Keychain or environment.\n"
        message << GitHub.pat_blurb
        super message
      end
    end

    # Error when the API returns a validation error.
    class ValidationFailedError < Error
      def initialize(github_message, errors)
        @github_message = if errors.empty?
          github_message
        else
          "#{github_message}: #{errors}"
        end

        super(@github_message)
      end
    end

    ERRORS = [
      AuthenticationFailedError,
      HTTPNotFoundError,
      RateLimitExceededError,
      Error,
      JSON::ParserError,
    ].freeze

    # Gets the password field from `git-credential-osxkeychain` for github.com,
    # but only if that password looks like a GitHub Personal Access Token.
    sig { returns(T.nilable(String)) }
    def keychain_username_password
      github_credentials = Utils.popen_write("git", "credential-osxkeychain", "get") do |pipe|
        pipe.write "protocol=https\nhost=github.com\n"
      end
      github_username = github_credentials[/username=(.+)/, 1]
      github_password = github_credentials[/password=(.+)/, 1]
      return unless github_username

      # Don't use passwords from the keychain unless they look like
      # GitHub Personal Access Tokens:
      #   https://github.com/Homebrew/brew/issues/6862#issuecomment-572610344
      return unless GITHUB_PERSONAL_ACCESS_TOKEN_REGEX.match?(github_password)

      github_password
    rescue Errno::EPIPE
      # The above invocation via `Utils.popen` can fail, causing the pipe to be
      # prematurely closed (before we can write to it) and thus resulting in a
      # broken pipe error. The root cause is usually a missing or malfunctioning
      # `git-credential-osxkeychain` helper.
      nil
    end

    def credentials
      @credentials ||= Homebrew::EnvConfig.github_api_token || keychain_username_password
    end

    sig { returns(Symbol) }
    def credentials_type
      if Homebrew::EnvConfig.github_api_token
        :env_token
      elsif keychain_username_password
        :keychain_username_password
      else
        :none
      end
    end

    # Given an API response from GitHub, warn the user if their credentials
    # have insufficient permissions.
    def credentials_error_message(response_headers, needed_scopes)
      return if response_headers.empty?

      scopes = response_headers["x-accepted-oauth-scopes"].to_s.split(", ")
      needed_scopes = Set.new(scopes || needed_scopes)
      credentials_scopes = response_headers["x-oauth-scopes"]
      return if needed_scopes.subset?(Set.new(credentials_scopes.to_s.split(", ")))

      needed_scopes = needed_scopes.to_a.join(", ").presence || "none"
      credentials_scopes = "none" if credentials_scopes.blank?

      what = case credentials_type
      when :keychain_username_password
        "macOS keychain GitHub"
      when :env_token
        "HOMEBREW_GITHUB_API_TOKEN"
      end

      @credentials_error_message ||= onoe <<~EOS
        Your #{what} credentials do not have sufficient scope!
        Scopes required: #{needed_scopes}
        Scopes present:  #{credentials_scopes}
        #{GitHub.pat_blurb}
      EOS
    end

    def open_rest(url, data: nil, data_binary_path: nil, request_method: nil, scopes: [].freeze, parse_json: true)
      # This is a no-op if the user is opting out of using the GitHub API.
      return block_given? ? yield({}) : {} if Homebrew::EnvConfig.no_github_api?

      # This is a Curl format token, not a Ruby one.
      # rubocop:disable Style/FormatStringToken
      args = ["--header", "Accept: application/vnd.github+json", "--write-out", "\n%{http_code}"]
      # rubocop:enable Style/FormatStringToken

      token = credentials
      args += ["--header", "Authorization: token #{token}"] unless credentials_type == :none
      args += ["--header", "X-GitHub-Api-Version:2022-11-28"]

      data_tmpfile = nil
      if data
        begin
          data = JSON.pretty_generate data
          data_tmpfile = Tempfile.new("github_api_post", HOMEBREW_TEMP)
        rescue JSON::ParserError => e
          raise Error, "Failed to parse JSON request:\n#{e.message}\n#{data}", e.backtrace
        end
      end

      if data_binary_path.present?
        args += ["--data-binary", "@#{data_binary_path}"]
        args += ["--header", "Content-Type: application/gzip"]
      end

      headers_tmpfile = Tempfile.new("github_api_headers", HOMEBREW_TEMP)
      begin
        if data_tmpfile
          data_tmpfile.write data
          data_tmpfile.close
          args += ["--data", "@#{data_tmpfile.path}"]

          args += ["--request", request_method.to_s] if request_method
        end

        args += ["--dump-header", T.must(headers_tmpfile.path)]

        output, errors, status = curl_output("--location", url.to_s, *args, secrets: [token])
        output, _, http_code = output.rpartition("\n")
        output, _, http_code = output.rpartition("\n") if http_code == "000"
        headers = headers_tmpfile.read
      ensure
        if data_tmpfile
          data_tmpfile.close
          data_tmpfile.unlink
        end
        headers_tmpfile.close
        headers_tmpfile.unlink
      end

      begin
        raise_error(output, errors, http_code, headers, scopes) if !http_code.start_with?("2") || !status.success?

        return if http_code == "204" # No Content

        output = JSON.parse output if parse_json
        if block_given?
          yield output
        else
          output
        end
      rescue JSON::ParserError => e
        raise Error, "Failed to parse JSON response\n#{e.message}", e.backtrace
      end
    end

    def paginate_rest(url, additional_query_params: nil, per_page: 100)
      (1..API_MAX_PAGES).each do |page|
        result = API.open_rest("#{url}?per_page=#{per_page}&page=#{page}&#{additional_query_params}")
        break if result.blank?

        yield(result, page)
      end
    end

    def open_graphql(query, variables: nil, scopes: [].freeze, raise_errors: true)
      data = { query: query, variables: variables }
      result = open_rest("#{API_URL}/graphql", scopes: scopes, data: data, request_method: "POST")

      if raise_errors
        if result["errors"].present?
          raise Error, result["errors"].map { |e| "#{e["type"]}: #{e["message"]}" }.join("\n")
        end

        result["data"]
      else
        result
      end
    end

    def raise_error(output, errors, http_code, headers, scopes)
      json = begin
        JSON.parse(output)
      rescue
        nil
      end
      message = json&.[]("message") || "curl failed! #{errors}"

      meta = {}
      headers.lines.each do |l|
        key, _, value = l.delete(":").partition(" ")
        key = key.downcase.strip
        next if key.empty?

        meta[key] = value.strip
      end

      credentials_error_message(meta, scopes)

      case http_code
      when "401"
        raise AuthenticationFailedError, message
      when "403"
        if meta.fetch("x-ratelimit-remaining", 1).to_i <= 0
          reset = meta.fetch("x-ratelimit-reset").to_i
          raise RateLimitExceededError.new(reset, message)
        end

        raise AuthenticationFailedError, message
      when "404"
        raise MissingAuthenticationError if credentials_type == :none && scopes.present?

        raise HTTPNotFoundError, message
      when "422"
        errors = json&.[]("errors") || []
        raise ValidationFailedError.new(message, errors)
      else
        raise Error, message
      end
    end
  end
end