# frozen_string_literal: true

require "net/http"
require "uri"
require "json"
require "securerandom"
require "fileutils"
require "digest"
require "base64"

require "dispatch/adapter/interface"

require_relative "claude/version"
require_relative "claude/errors"
require_relative "claude/token_store"
require_relative "claude/pkce"
require_relative "claude/oauth"
require_relative "claude/headers"
require_relative "claude/cloaking"
require_relative "claude/pricing_table"
require_relative "claude/model_catalog"
require_relative "claude/request_builder"
require_relative "claude/response_builder"
require_relative "claude/stream_collector"
require_relative "claude/sse_parser"
require_relative "claude/http_client"
require_relative "claude/usage_client"
require_relative "claude/rate_limit_headers"

module Dispatch
  module Adapter
    class Claude < Base
      VERSION = ClaudeVersion::VERSION

      DEFAULT_MODEL       = "claude-sonnet-4-5-20250929"
      MESSAGES_PATH       = "/v1/messages"
      COUNT_TOKENS_PATH   = "/v1/messages/count_tokens"
      MODELS_PATH         = "/v1/models"
      DEFAULT_BASE_URL    = "https://api.anthropic.com"

      # list_models cache TTL (1 hour in milliseconds)
      MODELS_CACHE_TTL_MS = 3_600_000

      # Keys that must be stripped before POSTing to count_tokens — the
      # endpoint rejects them with a 400 error.
      COUNT_TOKENS_STRIP_KEYS = %i[stream max_tokens metadata output_config].freeze

      # Default minimum interval between outbound requests (seconds).
      DEFAULT_MIN_REQUEST_INTERVAL = 1.0

      # @param model [String]       Anthropic model ID, e.g. "claude-sonnet-4-5-20250929"
      # @param api_key [String, nil] Raw API key or OAuth token; nil → load from
      #                              the TokenStore at initialization time.
      # @param token_path [String, nil]  Custom path for the OAuth token store file.
      #                                  Ignored when token_store: is also provided.
      # @param base_url [String]    API base URL (default: https://api.anthropic.com)
      # @param max_tokens [Integer, nil]  Instance-level default max_tokens for chat.
      # @param thinking [String, Hash, nil, false]  Instance-level default thinking config.
      #   Defaults to "high" so adaptive/extended thinking is enabled wherever
      #   the model supports it. Pass nil or false to disable, or pass a Hash
      #   like {type: :enabled, budget_tokens: 8000} for explicit budget mode.
      #   Per-call `thinking:` kwarg on chat() overrides this.
      # @param cache_retention [Symbol, nil]  Instance-level default cache retention.
      # @param user_agent_override [String, nil]  Custom User-Agent header value.
      # @param is_oauth [Boolean, nil]  Override OAuth detection; nil = auto-detect
      #                                 from token prefix.
      # @param token_store [TokenStore, nil]  Custom credential store (for testing).
      # @param extra_betas [Array<String>]  Additional beta header values.
      def initialize(
        model: DEFAULT_MODEL,
        api_key: nil,
        token_path: nil,
        base_url: DEFAULT_BASE_URL,
        max_tokens: nil,
        thinking: "high",
        cache_retention: nil,
        user_agent_override: nil,
        is_oauth: nil,
        token_store: nil,
        min_request_interval: DEFAULT_MIN_REQUEST_INTERVAL,
        rate_limit: nil,
        extra_betas: []
      )
        super()
        @model               = model.to_s
        @base_url            = base_url.to_s.chomp("/")
        @max_tokens          = max_tokens
        @thinking            = thinking
        @cache_retention     = cache_retention
        @user_agent_override = user_agent_override
        @extra_betas         = Array(extra_betas)
        @token_store         = token_store ||
                               (token_path ? TokenStore.new(path: token_path) : TokenStore.new)
        @is_oauth_override = is_oauth # nil = auto-detect

        # Track whether an explicit API key was supplied by the caller.
        # This distinguishes "has an explicit key" from "loaded from token store".
        @explicit_api_key = api_key && !api_key.to_s.strip.empty? ? api_key.to_s : nil

        # Resolve credentials at construction time so that later calls can
        # reliably inspect is_oauth? without triggering further I/O.
        @api_key = resolve_api_key(api_key)
        @is_oauth = resolve_is_oauth(@api_key, is_oauth)

        # When true, all subsequent requests skip strict tool-schema validation.
        # Set automatically when a "compiled grammar too large" 400 is received.
        @strict_disabled = false

        # Build the rate limiter using the same directory as the token store.
        rate_limit_path = File.join(File.dirname(@token_store.path), "claude_rate_limit")
        @rate_limiter = RateLimiter.new(
          rate_limit_path: rate_limit_path,
          min_request_interval: min_request_interval,
          rate_limit: rate_limit
        )

        # Stores the most recent parsed rate-limit headers (populated after
        # each chat/count_tokens/list_models call).
        @rate_limit_info = nil
        @last_all_headers = nil

        # Path for the JSONL debug log of rate-limit header snapshots.
        # Defaults to ~/.config/dispatch/claude_ratelimit.jsonl
        @rate_limit_log_path = File.join(File.dirname(@token_store.path), "claude_ratelimit.jsonl")
      end

      # ── Adapter interface ───────────────────────────────────────────────────

      def model_name
        @model
      end

      def provider_name
        "Anthropic (Claude)"
      end

      # Returns the context window size for the current model, or nil if unknown.
      #
      # @return [Integer, nil]
      def max_context_tokens
        PricingTable.context_window(@model)
      end

      # Returns the most recently captured rate-limit header info, or nil if
      # no API call has been made yet.
      #
      # @return [RateLimitHeaders::Info, nil]
      attr_reader :rate_limit_info

      # Returns ALL response headers from the most recent API call, as a Hash.
      # Useful for diagnosing which headers Anthropic actually sends.
      #
      # @return [Hash{String => String}, nil]
      attr_reader :last_response_headers

      # ── Auth lifecycle ──────────────────────────────────────────────────────

      # Ensure valid credentials are present, performing interactive login or
      # token refresh as needed.
      #
      # Returns:
      #   :api_key    — an explicit API key was supplied; nothing to do.
      #   :cached     — a non-expired OAuth token is already stored.
      #   :refreshed  — the stored token was expired; it was refreshed.
      #   :logged_in  — no credentials existed; interactive OAuth flow completed.
      #
      # @return [Symbol]
      def authenticate!
        return :api_key if explicit_api_key_present?

        creds = @token_store.load
        if creds && !expired?(creds)
          @api_key = creds["access_token"]
          @is_oauth = resolve_is_oauth(@api_key, @is_oauth_override)
          return :cached
        end

        if creds && creds["refresh_token"]
          refreshed = OAuth.refresh!(creds["refresh_token"])
          @token_store.save(creds.merge(refreshed))
          @api_key = refreshed["access_token"]
          @is_oauth = resolve_is_oauth(@api_key, @is_oauth_override)
          return :refreshed
        end

        fresh = OAuth.login(token_store: @token_store)
        @token_store.save(fresh)
        @api_key = fresh["access_token"]
        @is_oauth = resolve_is_oauth(@api_key, @is_oauth_override)
        :logged_in
      end

      # True iff the adapter has a usable credential (explicit key or stored token).
      #
      # @return [Boolean]
      def authenticated?
        return true if explicit_api_key_present?

        creds = @token_store.load
        !!(creds && creds["access_token"])
      end

      # Remove stored OAuth credentials and clear the in-memory token.
      # Has no effect when using an explicit API key.
      #
      # @return [nil]
      def logout!
        @token_store.delete
        @api_key = nil
        @is_oauth = false
        nil
      end

      def list_models
        now = current_time_ms
        return @models_cache if @models_cache && (now - @models_cache_at) < MODELS_CACHE_TTL_MS

        with_rate_limit do
          runtime_list = fetch_runtime_models
          models = merge_model_lists(runtime_list)

          @models_cache    = models
          @models_cache_at = current_time_ms
          models
        end
      end

      # Count the input tokens for a hypothetical chat request without
      # generating a response.  Uses Anthropic's dedicated endpoint
      # `POST /v1/messages/count_tokens`.
      #
      # @param messages [Array<Message>]
      # @param system   [String, Array, nil]
      # @param tools    [Array, nil]
      # @return [Integer] token count, or -1 on any error
      def count_tokens(messages, system: nil, tools: [])
        with_rate_limit do
          params = RequestBuilder.build(
            model_id: @model,
            messages: Array(messages),
            system: system,
            tools: Array(tools),
            is_oauth: @is_oauth,
            base_url: @base_url,
            stream: false,
            max_tokens: nil,
            thinking: nil,
            tool_choice: nil,
            cache_retention: nil,
            metadata: nil,
            disable_strict_tools: false
          )

          # Strip fields that count_tokens rejects.
          COUNT_TOKENS_STRIP_KEYS.each { |k| params.delete(k) }

          json = http_client(stream: false).post_json(COUNT_TOKENS_PATH, params)
          json["input_tokens"].to_i
        end
      rescue StandardError
        -1
      end

      # Fetch subscription usage (OAuth-only).
      #
      # @return [UsageReport, nil]
      def usage_report
        with_rate_limit do
          with_auth_recovery do
            ensure_token!
            UsageClient.fetch(
              http_client_claude_code,
              is_oauth: @is_oauth,
              on_rate_limit: method(:rotate_token_for_usage).to_proc
            )
          end
        end
      end

      # Send a chat request.
      #
      # When `stream: false` (default) the full response is buffered and a
      # Response is returned.  When `stream: true` the SSE events drive the
      # StreamCollector; deltas are yielded to the block.
      #
      # `thinking: :default` and `cache_retention: :default` resolve to
      # the instance-level defaults set at construction time.
      #
      # On a 400 "compiled grammar too large" / "schema too complex" error,
      # the request is automatically retried once with strict tool schemas
      # disabled, and `@strict_disabled` is set for all subsequent calls.
      def chat(
        messages,
        system: nil,
        tools: [],
        stream: false,
        max_tokens: nil,
        thinking: :default,
        tool_choice: nil,
        cache_retention: :default,
        metadata: nil,
        betas: nil, # rubocop:disable Lint/UnusedMethodArgument
        &block
      )
        with_rate_limit do
          with_auth_recovery do
            ensure_token!

            # Resolve :default sentinels to instance-level defaults.
            effective_thinking        = thinking == :default ? @thinking : thinking
            effective_cache_retention = cache_retention == :default ? @cache_retention : cache_retention
            effective_max_tokens      = max_tokens || @max_tokens

            params = build_chat_params(
              messages: messages,
              system: system,
              tools: tools,
              stream: stream,
              max_tokens: effective_max_tokens,
              thinking: effective_thinking,
              tool_choice: tool_choice,
              cache_retention: effective_cache_retention,
              metadata: metadata,
              disable_strict_tools: @strict_disabled
            )

            if stream
              chat_streaming_with_strict_fallback(params, messages, system, tools, stream,
                                                  effective_max_tokens, effective_thinking,
                                                  tool_choice, effective_cache_retention,
                                                  metadata, &block)
            else
              chat_non_streaming_with_strict_fallback(params, messages, system, tools, stream,
                                                      effective_max_tokens, effective_thinking,
                                                      tool_choice, effective_cache_retention,
                                                      metadata)
            end
          end
        end
      end

      # ── Streaming constants ───────────────────────────────────────────────

      # Maximum time (ms) to wait for the first SSE message_start event.
      # Reads the env var at load time; tests may override via stubbing
      # `stream_first_event_timeout_ms`.
      STREAM_FIRST_EVENT_TIMEOUT_MS = ENV.fetch("STREAM_FIRST_EVENT_TIMEOUT_MS", 60_000).to_i.freeze

      # Retry policy constants.
      STREAM_MAX_RETRIES   = 3
      STREAM_BASE_DELAY_MS = 2_000

      private

      # ── Strict-fallback helpers ───────────────────────────────────────────

      # Returns true iff the error is a 400 RequestError whose message
      # indicates the compiled grammar was too large or the schema was too
      # complex to compile.
      def strict_grammar_error?(err)
        return false unless err.is_a?(RequestError) && err.status_code == 400

        msg = err.message.to_s
        !!(
          (msg.match?(/compiled grammar/i) && msg.match?(/too large/i)) ||
            (msg.match?(/schema/i) && msg.match?(/too complex/i) && msg.match?(/compil/i))
        )
      end

      # Build request params, extracting common logic used in both the initial
      # attempt and the strict-fallback retry.
      def build_chat_params(messages:, system:, tools:, stream:,
                            max_tokens:, thinking:, tool_choice:,
                            cache_retention:, metadata:, disable_strict_tools:)
        RequestBuilder.build(
          model_id: @model,
          messages: Array(messages),
          system: system,
          tools: Array(tools),
          is_oauth: @is_oauth,
          base_url: @base_url,
          stream: stream ? true : false,
          max_tokens: max_tokens,
          thinking: thinking,
          tool_choice: tool_choice,
          cache_retention: cache_retention,
          metadata: metadata,
          disable_strict_tools: disable_strict_tools
        )
      end

      # Non-streaming chat with automatic strict-tool fallback on grammar errors.
      def chat_non_streaming_with_strict_fallback(params, messages, system, tools, stream,
                                                  max_tokens, thinking, tool_choice,
                                                  cache_retention, metadata)
        capture_cb = method(:capture_rate_limit_headers)
        json = http_client(stream: false).post_json(MESSAGES_PATH, params, on_response: capture_cb)
        model_info = ModelCatalog.build(@model)
        ResponseBuilder.build(json, model_info: model_info, is_oauth: @is_oauth)
      rescue RequestError => e
        raise unless strict_grammar_error?(e)

        # Disable strict tools permanently for this adapter instance.
        @strict_disabled = true

        # Rebuild params without strict tool schemas and retry once.
        fallback_params = build_chat_params(
          messages: messages, system: system, tools: tools,
          stream: stream, max_tokens: max_tokens, thinking: thinking,
          tool_choice: tool_choice, cache_retention: cache_retention,
          metadata: metadata, disable_strict_tools: true
        )
        json = http_client(stream: false).post_json(MESSAGES_PATH, fallback_params, on_response: capture_cb)
        model_info = ModelCatalog.build(@model)
        ResponseBuilder.build(json, model_info: model_info, is_oauth: @is_oauth)
      end

      # Streaming chat with automatic strict-tool fallback on grammar errors.
      def chat_streaming_with_strict_fallback(params, messages, system, tools, stream,
                                              max_tokens, thinking, tool_choice,
                                              cache_retention, metadata, &)
        chat_streaming(params, &)
      rescue RequestError => e
        raise unless strict_grammar_error?(e)

        # Disable strict tools permanently for this adapter instance.
        @strict_disabled = true

        # Rebuild params without strict tool schemas and retry once.
        fallback_params = build_chat_params(
          messages: messages, system: system, tools: tools,
          stream: stream, max_tokens: max_tokens, thinking: thinking,
          tool_choice: tool_choice, cache_retention: cache_retention,
          metadata: metadata, disable_strict_tools: true
        )
        chat_streaming(fallback_params, &)
      end

      # ── Internal helpers ──────────────────────────────────────────────────

      # Streaming chat path.  Yields StreamDelta events to the caller block
      # and returns a Response when the stream is complete.
      #
      # The SSE parser drives the StreamCollector.  Transient failures that
      # occur before any content has been emitted to the consumer are retried
      # up to STREAM_MAX_RETRIES times with exponential back-off.
      def chat_streaming(params, &block)
        attempt = 0

        loop do
          collector      = StreamCollector.new(@model, is_oauth: @is_oauth)
          parser         = SseParser.new
          retry_reason   = nil
          last_error     = nil

          begin
            deadline_ms        = stream_first_event_timeout_ms
            request_started_at = current_time_ms

            http_client(stream: true).stream(MESSAGES_PATH, params) do |response|
              ClaudeErrors.handle_response!(response) unless response.is_a?(Net::HTTPSuccess)
              capture_rate_limit_headers(response)
              response.read_body do |chunk|
                # Watchdog: abort if message_start hasn't arrived in time.
                if !collector.saw_message_start? &&
                   (current_time_ms - request_started_at) > deadline_ms
                  retry_reason = :first_event_timeout
                  raise RetriableStreamError, "first-event timeout (#{deadline_ms}ms)"
                end

                parser.feed(chunk) do |event_type, data|
                  collector.handle(event_type, data, &block)
                end
              end
              parser.flush
            end

            # ── Post-stream integrity checks ──────────────────────────────
            unless collector.saw_message_start?
              retry_reason = :no_message_start
              raise RetriableStreamError, "stream ended before message_start"
            end

            unless collector.saw_terminal?
              retry_reason = :no_terminal
              raise RetriableStreamError, "stream ended before message_stop/message_delta"
            end
          rescue RetriableStreamError => e
            last_error = e
            # fall through to retry decision below
          rescue RequestError, ConnectionError => e
            # An HTTP-level RequestError (status_code present) must surface
            # immediately — it may be a strict-grammar 400 that the caller
            # wants to catch, or a genuine 4xx that should not be retried.
            raise e if e.is_a?(RequestError) && e.status_code

            # A parse error or network error — only retry if no output yet.
            last_error = e
            retry_reason = if collector.consumer_output?
                             nil # not safe to retry
                           else
                             :parse_error
                           end
          rescue RateLimitError, ServerError, OverloadedError => e
            # Transient HTTP errors — retry if no consumer output yet.
            last_error = e
            retry_reason = if collector.consumer_output?
                             nil
                           else
                             :transient_http
                           end
          rescue StandardError => e
            last_error = e
            retry_reason = nil # non-retriable
          end

          # ── Retry decision ────────────────────────────────────────────────
          if retry_reason && attempt < STREAM_MAX_RETRIES
            attempt += 1
            sleep_ms = STREAM_BASE_DELAY_MS * (2**(attempt - 1))
            sleep(sleep_ms / 1000.0)
            next
          end

          # ── Success or give-up ────────────────────────────────────────────
          if last_error && retry_reason
            # Give up after exhausting retries: build an error response
            model_info = ModelCatalog.build(@model)
            usage = Usage.new(input_tokens: 0, output_tokens: 0)
            usage.cost = Pricing.calculate(usage, model_info)
            return Response.new(
              model: @model,
              stop_reason: :error,
              usage: usage
            )
          end

          if last_error && !retry_reason
            # Non-retriable or consumer output present — surface the error
            raise last_error
          end

          # ── Build successful Response ─────────────────────────────────────
          model_info = ModelCatalog.build(collector.model)
          u = collector.usage
          usage = Usage.new(
            input_tokens: u[:input],
            output_tokens: u[:output],
            cache_read_tokens: u[:cache_read],
            cache_creation_tokens: u[:cache_creation]
          )
          usage.cost = Pricing.calculate(usage, model_info)

          content_blocks, tool_calls = build_response_content(collector.content_blocks)
          stop_reason = ResponseBuilder::STOP_REASON_MAP.fetch(
            collector.finish_reason.to_s, :end_turn
          )

          return Response.new(
            model: collector.model,
            stop_reason: stop_reason,
            content: content_blocks,
            tool_calls: tool_calls,
            usage: usage
          )
        end
      end

      # Build content blocks and tool_calls arrays from the StreamCollector's
      # accumulated content_blocks.  Mirrors the logic in ResponseBuilder but
      # operates on the collector's internal Hash format rather than raw JSON.
      #
      # @param blocks [Array<Hash>]  collector.content_blocks
      # @return [Array(Array, Array)]  [content_blocks, tool_calls]
      def build_response_content(blocks)
        content    = []
        tool_calls = []

        blocks.each do |blk|
          case blk[:kind]
          when "text"
            text = blk[:text].to_s
            content << TextBlock.new(text: text) unless text.empty?

          when "thinking"
            thinking  = blk[:thinking].to_s
            signature = blk[:signature]
            content << ThinkingBlock.new(thinking: thinking, signature: signature)

          when "redacted_thinking"
            data = blk[:data].to_s
            content << RedactedThinkingBlock.new(data: data) unless data.empty?

          when "tool_use"
            tool_calls << ToolUseBlock.new(
              id: blk[:id].to_s,
              name: blk[:name].to_s,
              arguments: blk[:arguments] || {}
            )
          end
        end

        [content, tool_calls]
      end

      # Simple marker error class for internally-flagged retry scenarios.
      class RetriableStreamError < StandardError; end
      private_constant :RetriableStreamError

      # Returns current monotonic time in milliseconds.
      # Extracted as a method so specs can stub it.
      def current_time_ms
        Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
      end

      # Returns the configured first-event timeout in milliseconds.
      # Extracted as a method so specs can stub it.
      def stream_first_event_timeout_ms
        STREAM_FIRST_EVENT_TIMEOUT_MS
      end

      # ── list_models helpers ───────────────────────────────────────────────

      # Fetch the runtime model list from GET /v1/models.
      # Returns an Array<Hash> (the "data" entries) or [] on any error.
      def fetch_runtime_models
        json = http_client(stream: false).get_json("#{MODELS_PATH}?limit=200")
        Array(json["data"])
      rescue StandardError
        []
      end

      # Merge runtime entries with the bundled list.
      # Runtime models override the bundled name; entirely new models are
      # appended with pricing: nil.
      def merge_model_lists(runtime_entries)
        return PricingTable.known_ids.map { |id| ModelCatalog.build(id) } if runtime_entries.empty?

        seen_ids = {}
        result   = []

        # Build from runtime entries (order preserved)
        runtime_entries.each do |entry|
          id = entry["id"].to_s
          next if id.empty?

          seen_ids[id] = true
          result << ModelCatalog.build_from_api(entry)
        end

        # Append any bundled models not present in the runtime response
        PricingTable.known_ids.each do |id|
          next if seen_ids[id]

          result << ModelCatalog.build(id)
        end

        result
      end

      # Build (or reuse) an HttpClient for the given stream mode.
      # The headers_proc is evaluated fresh on every request so that OAuth
      # token refreshes are picked up without restarting.
      def http_client(stream: false) # rubocop:disable Lint/UnusedMethodArgument
        HttpClient.new(
          base_url: @base_url,
          headers_proc: build_headers_proc
        )
      end

      # Build an HttpClient that emits the real-Claude-Code header set
      # (no anthropic-version, no x-stainless-*). Required for /api/oauth/*
      # endpoints which reject SDK-style requests with
      # "OAuth authentication is currently not supported."
      def http_client_claude_code
        HttpClient.new(
          base_url: @base_url,
          headers_proc: build_headers_proc(claude_code_only: true)
        )
      end

      # Returns a Proc that, when called with `stream: <bool>`, yields the
      # correct headers.  Called fresh per-request so that a token refresh
      # is automatically picked up.
      def build_headers_proc(claude_code_only: false)
        adapter     = self
        base_url    = @base_url
        extra_betas = @extra_betas
        cc_only     = claude_code_only

        lambda do |stream: false|
          Headers.build(
            api_key: adapter.instance_variable_get(:@api_key),
            is_oauth: adapter.instance_variable_get(:@is_oauth),
            stream: stream,
            base_url: base_url,
            extra_betas: extra_betas,
            claude_code_only: cc_only
          )
        end
      end

      # Resolve the API key: prefer the explicitly-supplied value, then fall
      # back to the TokenStore (OAuth creds).
      def resolve_api_key(explicit_key)
        return explicit_key.to_s if explicit_key && !explicit_key.to_s.strip.empty?

        creds = @token_store.load
        creds&.fetch("access_token", nil)
      end

      # Decide if this is an OAuth session.
      def resolve_is_oauth(api_key, override)
        return override unless override.nil?

        api_key.to_s.start_with?("sk-ant-oat")
      end

      # ── Auth helpers ──────────────────────────────────────────────────────

      # True iff an explicit API key was supplied at construction time.
      def explicit_api_key_present?
        !@explicit_api_key.nil?
      end

      # Throttle an outbound API call through the RateLimiter.
      def with_rate_limit
        @rate_limiter&.wait!
        yield
      end

      # ── Rate-limit header capture ─────────────────────────────────────────

      # Parse rate-limit unified headers from a Net::HTTP response, store the
      # result in @rate_limit_info, and append a JSON entry to the debug log.
      #
      # Errors are silently swallowed — header capture must never affect the
      # main request flow.
      def capture_rate_limit_headers(response)
        # Always log ALL response headers for debugging (one line to stderr).
        all_headers = {}
        response.each_header { |k, v| all_headers[k] = v } if response.respond_to?(:each_header)
        @last_all_headers = all_headers

        info = RateLimitHeaders.parse(response)
        return unless info

        @rate_limit_info = info
        log_rate_limit_info(info)
      rescue StandardError
        # Never raise — this is best-effort instrumentation only.
      end

      # Append a single JSON line to the rate-limit JSONL debug log.
      def log_rate_limit_info(info)
        FileUtils.mkdir_p(File.dirname(@rate_limit_log_path))
        entry = info.to_log_hash.merge(model: @model)
        File.open(@rate_limit_log_path, "a") { |f| f.puts(JSON.generate(entry)) }
      rescue StandardError
        # Best-effort.
      end

      # True iff the stored credentials have an expired (or absent) expiry.
      # Treats missing/zero expires_at_ms as expired.
      def expired?(creds)
        expires_at_ms = creds["expires_at_ms"].to_i
        return true if expires_at_ms.zero?

        now_ms = (Time.now.to_f * 1000).to_i
        now_ms >= expires_at_ms
      end

      # Wrap a block such that an AuthenticationError (server-revoked
      # access token, refresh-token rejection, etc.) triggers a single
      # automatic recovery cycle:
      #   1. Wipe the stored credentials.
      #   2. Run the full interactive OAuth login flow (opens browser).
      #   3. Retry the block once with the fresh token.
      #
      # Disabled for explicit-API-key callers (no OAuth fallback exists).
      # Disabled when AUTH_RECOVERY env var is set to "0" (for tests / CI).
      def with_auth_recovery
        return yield if explicit_api_key_present?
        return yield if ENV["AUTH_RECOVERY"] == "0"

        attempts = 0
        begin
          attempts += 1
          yield
        rescue AuthenticationError
          raise if attempts > 1

          warn "[claude] authentication failed (token may have been revoked); " \
               "re-running OAuth login..."
          @token_store.delete
          fresh = OAuth.login(token_store: @token_store)
          @token_store.save(fresh)
          @api_key  = fresh["access_token"]
          @is_oauth = resolve_is_oauth(@api_key, @is_oauth_override)
          retry
        end
      end

      # Force-rotate the OAuth access token by performing a refresh-token
      # exchange. Used as the on_rate_limit callback for /api/oauth/usage,
      # which enforces a per-access-token quota: each fresh token gets
      # ~5 calls before persistent 429. Rotating gets us a fresh window.
      #
      # Returns true on success, false otherwise.
      def rotate_token_for_usage
        return false if explicit_api_key_present?

        creds = @token_store.load
        refresh_token = creds && creds["refresh_token"]
        return false unless refresh_token

        refreshed = OAuth.refresh!(refresh_token)
        @token_store.save(creds.merge(refreshed))
        @api_key = refreshed["access_token"]
        @is_oauth = resolve_is_oauth(@api_key, @is_oauth_override)
        true
      rescue StandardError
        false
      end

      # Lazily refreshes the OAuth token when it is within 5 minutes of
      # expiry.  No-op when using an explicit API key or when the token is
      # still fresh.
      def ensure_token!
        return if explicit_api_key_present?

        creds = @token_store.load
        return unless creds
        return unless expired?(creds)
        return unless creds["refresh_token"]

        refreshed = OAuth.refresh!(creds["refresh_token"])
        @token_store.save(creds.merge(refreshed))
        @api_key = refreshed["access_token"]
        @is_oauth = resolve_is_oauth(@api_key, @is_oauth_override)
      rescue StandardError
        # Silently swallow errors in ensure_token! — the request will
        # likely fail with an auth error, which is more informative.
        nil
      end
    end
  end
end