defmodule Ragex.CLI.Chat do
  @moduledoc """
  Interactive terminal chat UI for codebase Q&A using the Ragex agent.

  Each user question is handled by the agent executor (ReAct loop) which
  actively calls Ragex MCP read-only query tools — `hybrid_search`,
  `semantic_search`, `read_file`, `query_graph`, `find_callers`, etc. —
  to retrieve relevant code context before composing the answer.  The
  restricted tool set (`ToolSchema.rag_query_tools/1`) prevents the AI from
  accidentally re-triggering heavy analysis pipelines while still giving it
  full read access to the knowledge graph and embeddings.

  Blocking `Core.chat/3` is used for every query (rather than streaming) so
  that tool-call responses are reliably captured.  Some providers (e.g.
  DeepSeek R1) emit content and tool_calls in the same response chunk; the
  streaming parser would silently drop the tool calls, truncating answers.

  The initial codebase analysis and first-run audit report are generated
  separately (via `Core.analyze_project/2` and `Core.stream_generate_report/3`)
  and use no tools (report generation) or the full agent tool set (re-analysis).

  ## Usage

      Ragex.CLI.Chat.start(path: "/path/to/project")

  ## Commands

  - `/help`    - Show available commands
  - `/history` - Show conversation history
  - `/clear`   - Clear conversation and start fresh
  - `/sources` - Show sources from last response (empty — agent tracks tool
                 call results internally, not as named sources)
  - `/analyze` - Re-analyze the codebase
  - `/status`  - Show session and graph stats
  - `/quit`    - Exit the chat
  """

  require Logger

  alias Ragex.Agent.{Core, Memory, ToolSchema}
  alias Ragex.AI.Config, as: AIConfig
  alias Ragex.Analysis.Cache, as: AnalysisCache
  alias Ragex.CLI.{Colors, Progress}
  alias Ragex.Graph.Store

  @spinner_frames ["⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"]

  @type state :: %{
          session_id: String.t() | nil,
          path: String.t(),
          provider: atom() | nil,
          model: String.t() | nil,
          strategy: atom(),
          last_sources: [map()],
          message_count: non_neg_integer(),
          analyzed: boolean()
        }

  @doc """
  Start an interactive chat session.

  Runs the initial codebase analysis (unless `:skip_analysis` is true),
  streams the opening audit report, then enters an interactive loop where
  every question is answered by the agent executor using Ragex MCP query tools.

  ## Options

  - `:path` - Project path to analyze (default: cwd)
  - `:provider` - AI provider atom (default: configured default)
  - `:model` - Model name override
  - `:strategy` - Accepted for compatibility but not used; queries always go
                  through the agent ReAct loop rather than the retrieval pipeline
  - `:skip_analysis` - Skip initial analysis (default: false)
  - `:include_dead_code` - Enable dead code analysis (default: false)
  - `:debug` - Print tool-call details and session messages to stderr (default: false)
  """
  @spec start(keyword()) :: :ok
  def start(opts \\ []) do
    path = opts |> Keyword.get_lazy(:path, fn -> File.cwd!() end) |> Path.expand()
    provider = Keyword.get(opts, :provider)
    model = Keyword.get(opts, :model)
    strategy = Keyword.get(opts, :strategy, :fusion)
    skip_analysis = Keyword.get(opts, :skip_analysis, false)
    include_dead_code = Keyword.get(opts, :include_dead_code, false)

    debug = Keyword.get(opts, :debug, false)

    state = %{
      session_id: nil,
      path: path,
      provider: provider,
      model: model,
      strategy: strategy,
      last_sources: [],
      message_count: 0,
      analyzed: false,
      include_dead_code: include_dead_code,
      debug: debug
    }

    render_banner(state)

    state =
      if skip_analysis do
        # Check if graph already has data
        stats = Store.stats()

        if stats.nodes > 0 do
          IO.puts(
            Colors.info(
              "Skipping analysis (graph has #{stats.nodes} nodes, #{stats.edges} edges)"
            )
          )

          %{state | analyzed: true}
        else
          IO.puts(Colors.warning("No graph data found. Running initial analysis..."))
          run_analysis(state)
        end
      else
        run_analysis(state)
      end

    IO.puts("")
    IO.puts(Colors.muted("Type your question or /help for commands."))
    IO.puts("")

    chat_loop(state)
  end

  # Private functions

  defp chat_loop(state) do
    prompt = build_prompt(state)

    case IO.gets(prompt) do
      :eof ->
        shutdown(state)

      {:error, _reason} ->
        shutdown(state)

      input when is_binary(input) ->
        input = String.trim(input)
        handle_input(input, state)
    end
  end

  defp handle_input("", state), do: chat_loop(state)
  defp handle_input("/quit", state), do: shutdown(state)
  defp handle_input("/exit", state), do: shutdown(state)
  defp handle_input("/q", state), do: shutdown(state)

  defp handle_input("/help", state) do
    render_help()
    chat_loop(state)
  end

  defp handle_input("/history", state) do
    render_history(state)
    chat_loop(state)
  end

  defp handle_input("/clear", state) do
    if state.session_id, do: Memory.clear_session(state.session_id)
    IO.puts(Colors.info("Conversation cleared."))
    state = %{state | session_id: nil, message_count: 0, last_sources: []}
    chat_loop(state)
  end

  defp handle_input("/sources", state) do
    render_sources(state.last_sources)
    chat_loop(state)
  end

  defp handle_input("/analyze", state) do
    state = run_analysis(state)
    chat_loop(state)
  end

  defp handle_input("/status", state) do
    render_status(state)
    chat_loop(state)
  end

  defp handle_input("/" <> unknown, state) do
    IO.puts(Colors.error("Unknown command: /#{unknown}. Type /help for available commands."))
    chat_loop(state)
  end

  defp handle_input(query, state) do
    state = process_query(query, state)
    chat_loop(state)
  end

  defp process_query(query, state) do
    query_start = System.monotonic_time(:millisecond)

    # Ensure a session exists before calling Core.chat
    state = ensure_session(state)

    # Use the agent executor with Ragex MCP query tools for RAG.
    # Blocking Core.chat is used (not stream_chat) because the ReAct loop
    # must capture tool_call responses from the LLM; streaming parsers can drop
    # tool_call deltas on providers like DeepSeek R1 that return content + calls
    # simultaneously.
    spinner = start_phase_timer("Thinking...")

    if state.debug, do: IO.puts(:stderr, Colors.muted("[debug] agent chat with Ragex MCP tools"))

    # Restrict to read-only RAG query tools so the AI can look up evidence
    # from the existing knowledge graph without re-triggering heavy analysis
    # pipelines (analyze_directory, find_dead_code, find_duplicates, etc.).
    rag_tools = ToolSchema.rag_query_tools(state.provider || :openai)

    chat_opts =
      [
        system_prompt_override: conversation_system_prompt(state.path),
        tools: rag_tools
      ]
      |> maybe_add(:provider, state.provider)
      |> maybe_add(:model, state.model)

    result = Core.chat(state.session_id, query, chat_opts)
    stop_phase_timer(spinner)

    elapsed = System.monotonic_time(:millisecond) - query_start

    case result do
      {:ok, %{content: content, tool_calls_made: tc}} ->
        if state.debug do
          IO.puts(:stderr, Colors.muted("[debug] tool calls made: #{tc}"))
          dump_session_messages(state.session_id)
        end

        if content != "" do
          IO.puts("")
          IO.puts(Marcli.render(content))
        end

        IO.puts("")

        IO.puts(
          Colors.success("\u2713") <>
            Colors.muted(" Done (#{Progress.format_elapsed(elapsed)})")
        )

        IO.puts("")

        # Messages are already tracked by Core.chat -> only update UI state
        %{state | last_sources: [], message_count: state.message_count + 1}

      {:error, {:rate_limited, reason}} ->
        IO.puts("")
        IO.puts(Colors.error("Rate limited: #{reason}"))

        IO.puts(
          Colors.muted("Wait a moment and try again. (#{Progress.format_elapsed(elapsed)})")
        )

        IO.puts("")
        state

      {:error, reason} ->
        IO.puts("")

        IO.puts(
          Colors.error("Error: #{inspect(reason)}") <>
            Colors.muted(" (#{Progress.format_elapsed(elapsed)})")
        )

        IO.puts("")
        state
    end
  end

  defp run_analysis(state) do
    IO.puts("")

    # Show cache status before analysis
    graph_stats = Store.stats()

    cache_status =
      if graph_stats.nodes > 0 do
        case AnalysisCache.load(state.path) do
          {:ok, _} ->
            IO.puts(
              Colors.info(
                "Cache hit: #{graph_stats.nodes} nodes, #{graph_stats.edges} edges loaded. All files unchanged."
              )
            )

            :fresh

          {:stale, _, changed} ->
            IO.puts(
              Colors.info(
                "Partial cache: #{graph_stats.nodes} nodes loaded. #{length(changed)} files changed, updating..."
              )
            )

            :stale

          _ ->
            :miss
        end
      else
        :miss
      end

    label =
      case cache_status do
        :fresh -> "Restoring from cache..."
        :stale -> "Incremental analysis..."
        :miss -> "Analyzing #{Path.basename(state.path)}..."
      end

    spinner = start_spinner(label)

    # Phase 1: Analysis (skip report generation for streaming)
    analysis_opts = [
      skip_embeddings: false,
      include_dead_code: state.include_dead_code,
      skip_report: true
    ]

    case Core.analyze_project(state.path, analysis_opts) do
      {:ok, result} ->
        stop_spinner(spinner, nil)

        summary_text = format_analysis_summary(result.summary)

        box =
          Owl.Box.new(summary_text,
            title: "Analysis Complete",
            border_style: :solid_rounded,
            border_tag: :green,
            padding_x: 1,
            padding_y: 0
          )

        Owl.IO.puts(box)

        # Phase 2: Stream the AI report generation
        state = stream_initial_report(state, result.issues)

        %{state | analyzed: true}

      {:error, reason} ->
        stop_spinner(spinner, nil)
        IO.puts(Colors.error("Analysis failed: #{inspect(reason)}"))
        IO.puts(Colors.muted("You can still ask questions if the graph has data."))

        # Check existing graph data
        stats = Store.stats()

        if stats.nodes > 0 do
          %{state | analyzed: true}
        else
          state
        end
    end
  end

  defp stream_initial_report(state, issues) do
    report_spinner = start_phase_timer("Generating report")
    {:ok, spinner_stopped} = Agent.start_link(fn -> false end)

    # The on_chunk callback is fired once by Core.stream_generate_report after
    # the blocking executor run completes.  Its only job here is to stop the
    # spinner; the content is rendered via Marcli below, avoiding double output.
    on_chunk = fn
      %{content: text} when is_binary(text) and text != "" ->
        unless Agent.get(spinner_stopped, & &1) do
          stop_phase_timer(report_spinner)
          Agent.update(spinner_stopped, fn _ -> true end)
        end

      _ ->
        :ok
    end

    report_opts =
      [on_chunk: on_chunk]
      |> maybe_add(:provider, state.provider)
      |> maybe_add(:model, state.model)

    case Core.stream_generate_report(state.path, issues, report_opts) do
      {:ok, content, _ai_status} ->
        unless Agent.get(spinner_stopped, & &1) do
          stop_phase_timer(report_spinner)
        end

        Agent.stop(spinner_stopped)

        if content != "" do
          IO.puts("")
          IO.puts(Marcli.render(content))
          IO.puts("")
        end

        # Core.stream_generate_report created a session; capture its ID
        case Core.list_sessions(limit: 1) do
          [%{id: session_id} | _] -> %{state | session_id: session_id}
          _ -> state
        end

      {:error, reason} ->
        unless Agent.get(spinner_stopped, & &1) do
          stop_phase_timer(report_spinner)
        end

        Agent.stop(spinner_stopped)
        IO.puts(Colors.error("Report generation failed: #{inspect(reason)}"))
        state
    end
  end

  defp ensure_session(%{session_id: nil} = state) do
    case Memory.new_session(%{project_path: state.path}) do
      {:ok, session} -> %{state | session_id: session.id}
    end
  end

  defp ensure_session(state), do: state

  # Rendering

  defp render_banner(state) do
    project_name = Path.basename(state.path)

    provider_info =
      if state.provider do
        "Provider: #{state.provider}"
      else
        "Provider: #{AIConfig.provider_name()}"
      end

    model_info =
      if state.model do
        "Model: #{state.model}"
      else
        ""
      end

    info_lines =
      [
        "Project: #{project_name}",
        "Path: #{state.path}",
        provider_info,
        model_info,
        "Strategy: #{state.strategy}"
      ]
      |> Enum.reject(&(&1 == ""))
      |> Enum.join("\n")

    box =
      Owl.Box.new(info_lines,
        title: "Ragex Chat",
        border_style: :solid_rounded,
        border_tag: :cyan,
        padding_x: 1,
        padding_y: 0
      )

    IO.puts("")
    Owl.IO.puts(box)
  end

  defp render_help do
    commands = """
    /help      Show this help message
    /history   Show conversation history
    /clear     Clear conversation and start fresh
    /sources   Show sources from last response
    /analyze   Re-analyze the codebase
    /status    Show session and graph stats
    /quit      Exit the chat
    """

    box =
      Owl.Box.new(commands,
        title: "Commands",
        border_style: :solid_rounded,
        border_tag: :cyan,
        padding_x: 1,
        padding_y: 0
      )

    IO.puts("")
    Owl.IO.puts(box)
    IO.puts("")
  end

  defp render_history(%{session_id: nil}) do
    IO.puts(Colors.muted("No conversation history yet."))
  end

  defp render_history(%{session_id: session_id}) do
    case Memory.get_messages(session_id) do
      {:ok, messages} when messages != [] ->
        IO.puts("")

        Enum.each(messages, fn msg ->
          render_history_message(msg)
        end)

        IO.puts("")

      _ ->
        IO.puts(Colors.muted("No conversation history yet."))
    end
  end

  defp render_history_message(%{role: :user, content: content}) do
    IO.puts(Colors.highlight("You: ") <> (content || ""))
  end

  defp render_history_message(%{role: :assistant, content: content}) do
    IO.puts(Colors.info("Ragex: ") <> (content || ""))
  end

  defp render_history_message(%{role: :system}) do
    # Skip system messages in display
    :ok
  end

  defp render_history_message(%{role: :tool, content: content, name: name}) do
    label = if name, do: "[tool:#{name}]", else: "[tool]"
    IO.puts(Colors.muted(label <> " ") <> (content || ""))
  end

  defp render_history_message(%{role: role, content: content}) do
    IO.puts(Colors.muted("[#{role}] ") <> (content || ""))
  end

  defp render_sources([]) do
    IO.puts(Colors.muted("No sources from last response."))
  end

  defp render_sources(sources) do
    IO.puts("")
    IO.puts(Colors.bold("Sources:"))

    Enum.each(sources, fn source ->
      file = source[:file] || "unknown"
      score = source[:score] || 0.0
      line = source[:line]

      location = if line, do: "#{file}:#{line}", else: file
      score_str = "#{Float.round(score * 100, 1)}%"

      IO.puts(
        "  " <>
          Colors.muted(score_str) <>
          " " <>
          Colors.highlight(Path.relative_to_cwd(location))
      )
    end)

    IO.puts("")
  end

  defp render_status(state) do
    raw_stats = Store.stats()
    modules = Store.list_nodes(:module)
    functions = Store.list_nodes(:function)

    session_info =
      if state.session_id do
        case Memory.get_session(state.session_id) do
          {:ok, session} -> "Messages: #{length(session.messages)}"
          _ -> "Session: expired"
        end
      else
        "Session: none"
      end

    info = """
    Graph Nodes:  #{raw_stats.nodes}
    Graph Edges:  #{raw_stats.edges}
    Embeddings:   #{raw_stats.embeddings}
    Modules:      #{length(modules)}
    Functions:    #{length(functions)}
    #{session_info}
    Analyzed:     #{state.analyzed}
    """

    box =
      Owl.Box.new(info,
        title: "Status",
        border_style: :solid_rounded,
        border_tag: :cyan,
        padding_x: 1,
        padding_y: 0
      )

    IO.puts("")
    Owl.IO.puts(box)
    IO.puts("")
  end

  defp format_analysis_summary(summary) do
    lines = [
      "Total Issues: #{summary.total_issues}",
      if(Map.get(summary, :quality_files_analyzed, 0) > 0,
        do: "Quality:      #{summary.quality_files_analyzed} files"
      ),
      if(summary.dead_code_count > 0, do: "Dead Code:    #{summary.dead_code_count}"),
      "Duplicates:   #{summary.duplicate_count}",
      "Security:     #{summary.security_count}",
      "Smells:       #{summary.smell_count}",
      "Complexity:   #{summary.complexity_count}"
    ]

    lines
    |> Enum.reject(&is_nil/1)
    |> Enum.join("\n")
  end

  defp build_prompt(state) do
    count =
      if state.message_count > 0 do
        Colors.muted("[#{state.message_count}] ")
      else
        ""
      end

    count <> Colors.highlight("ragex> ")
  end

  defp shutdown(state) do
    IO.puts("")
    IO.puts(Colors.muted("Goodbye!"))

    if state.session_id do
      Logger.debug("Chat session #{state.session_id} ended")
    end

    :ok
  end

  defp start_spinner(label) do
    Progress.start(label)
  end

  defp stop_spinner(pid, message) do
    Progress.stop(pid, message)
  end

  defp maybe_add(opts, _key, nil), do: opts
  defp maybe_add(opts, key, value), do: Keyword.put(opts, key, value)

  # Conversation system prompt for follow-up questions

  defp conversation_system_prompt(path) do
    """
    You are an expert code analysis assistant. The project at #{path} has been
    FULLY ANALYZED. The knowledge graph, embeddings, and all metrics are populated.

    CRITICAL RULES:
    1. The codebase is ALREADY analyzed. Do NOT call analyze_directory, analyze_quality,
       find_dead_code, find_duplicates, or scan_security. These re-run the full pipeline.
    2. Use Ragex MCP query tools to retrieve information from the knowledge graph and
       embeddings. Call as many tools as needed to give a thorough, accurate answer:
       - hybrid_search: best general-purpose code search (semantic + graph)
       - semantic_search: find code related to a topic by meaning
       - read_file: read actual source code from a specific file
       - query_graph: query the knowledge graph for module/function details
       - list_nodes: list modules or functions in the graph
       - find_callers: find what calls a specific function
       - find_paths: find dependency paths between modules
       - find_circular_dependencies: detect circular dependencies
       - coupling_report: get coupling metrics
       - graph_stats: get knowledge graph statistics
    3. Start with hybrid_search or semantic_search to locate relevant code before
       reading files or querying the graph.
    4. Be specific: cite file paths, function names, line numbers, code snippets.
    5. Respond in clear Markdown. Answer the specific question concisely.
    """
  end

  # Debug helpers

  defp dump_session_messages(session_id) do
    case Memory.get_messages(session_id) do
      {:ok, messages} ->
        IO.puts(:stderr, Colors.muted("[debug] Session messages (#{length(messages)}):"))

        Enum.each(messages, fn msg ->
          role = msg.role
          content = msg.content || ""
          preview = content |> String.slice(0, 200) |> String.replace("\n", " ")
          tool_info = if msg[:name], do: " [#{msg[:name]}]", else: ""

          IO.puts(
            :stderr,
            Colors.muted(
              "  [#{role}#{tool_info}] #{preview}#{if String.length(content) > 200, do: "...", else: ""}"
            )
          )
        end)

      _ ->
        :ok
    end
  end

  defp start_phase_timer(label) do
    if Colors.enabled?() do
      start_time = System.monotonic_time(:millisecond)

      spawn(fn ->
        phase_timer_loop(@spinner_frames, label, start_time, 0)
      end)
    else
      IO.puts(label <> "...")
      nil
    end
  end

  defp stop_phase_timer(nil), do: :ok

  defp stop_phase_timer(pid) when is_pid(pid) do
    if Process.alive?(pid) do
      ref = Process.monitor(pid)
      Process.exit(pid, :kill)

      receive do
        {:DOWN, ^ref, :process, ^pid, _} -> :ok
      after
        100 -> :ok
      end

      IO.write("\r\e[K")
    end

    :ok
  end

  defp phase_timer_loop(frames, phase, start_time, frame_index) do
    frame = Enum.at(frames, rem(frame_index, length(frames)))
    elapsed_ms = System.monotonic_time(:millisecond) - start_time
    elapsed_s = div(elapsed_ms, 1000)

    output = Colors.info(frame) <> " " <> phase <> Colors.muted(" (#{elapsed_s}s)")
    IO.write("\r\e[K" <> output)

    receive do
      {:update_phase, new_phase} ->
        phase_timer_loop(frames, new_phase, start_time, frame_index + 1)

      :stop ->
        :ok
    after
      80 ->
        phase_timer_loop(frames, phase, start_time, frame_index + 1)
    end
  end
end