"""Custom LLM client using httpx for Claude Messages API via third-party proxy.

The proxy does not support Claude's native tool_use format (it strips the `tools`
field from requests). So we embed tool definitions in the system prompt and parse
structured JSON tool calls from the model's text output (ReAct-style).
"""

from __future__ import annotations

import asyncio
import json
import logging
import os
import re
import time
from collections import Counter
from dataclasses import dataclass, field
from typing import Any

import httpx

logger = logging.getLogger(__name__)


class LLMAPIError(Exception):
    """Raised when the LLM API is unreachable after all retries."""

    def __init__(self, message: str, attempts: int) -> None:
        super().__init__(message)
        self.attempts = attempts


# Markers the model uses to signal tool calls and final answers
TOOL_CALL_TAG = "<tool_call>"
TOOL_CALL_END = "</tool_call>"
TOOL_RESULT_TAG = "<tool_result>"
TOOL_RESULT_END = "</tool_result>"
ANSWER_TAG = "<answer>"
ANSWER_END = "</answer>"


def _build_tools_prompt(tools: list[dict]) -> str:
    """Format tool definitions for inclusion in the system prompt."""
    lines = ["You have access to the following tools:\n"]
    for t in tools:
        schema = t.get("input_schema", {})
        props = schema.get("properties", {})
        required = schema.get("required", [])

        params = []
        for pname, pdef in props.items():
            req = " (required)" if pname in required else ""
            desc = pdef.get("description", "")
            ptype = pdef.get("type", "string")
            enum_vals = pdef.get("enum")
            if enum_vals:
                allowed = ", ".join(f'"{v}"' for v in enum_vals)
                params.append(f"    - {pname}: {ptype}{req} — {desc} Allowed values: [{allowed}]")
            else:
                params.append(f"    - {pname}: {ptype}{req} — {desc}")

        param_block = "\n".join(params) if params else "    (no parameters)"
        lines.append(f"## {t['name']}\n{t['description']}\nParameters:\n{param_block}\n")

    lines.append(
        "## How to use tools\n"
        "To call a tool, output a JSON block wrapped in XML tags like this:\n"
        f"{TOOL_CALL_TAG}\n"
        '{"name": "tool_name", "arguments": {"param1": "value1"}}\n'
        f"{TOOL_CALL_END}\n\n"
        "You can call multiple tools in sequence. After each tool call, you will receive the result in:\n"
        f"{TOOL_RESULT_TAG}\n...result...\n{TOOL_RESULT_END}\n\n"
        "When you have finished your analysis and have a final answer, wrap it in:\n"
        f"{ANSWER_TAG}\nyour final answer here\n{ANSWER_END}\n\n"
        "Think step by step. Call tools to gather evidence before drawing conclusions.\n"
        "You MUST call at least one tool before giving your final answer."
    )
    return "\n".join(lines)


def _extract_tool_calls(text: str) -> list[dict]:
    """Extract tool call JSON blocks from model output."""
    pattern = re.compile(
        re.escape(TOOL_CALL_TAG) + r"\s*(.*?)\s*" + re.escape(TOOL_CALL_END),
        re.DOTALL,
    )
    calls = []
    for match in pattern.finditer(text):
        raw = match.group(1).strip()
        try:
            parsed = json.loads(raw)
            calls.append(parsed)
        except json.JSONDecodeError:
            logger.warning("Failed to parse tool call JSON: %s", raw[:200])
    return calls


def _extract_answer(text: str) -> str | None:
    """Extract the final answer from model output."""
    pattern = re.compile(
        re.escape(ANSWER_TAG) + r"\s*(.*?)\s*" + re.escape(ANSWER_END),
        re.DOTALL,
    )
    match = pattern.search(text)
    if match:
        return match.group(1).strip()
    return None


def _truncate_tool_result(result_text: str, max_chars: int = 3000) -> str:
    """Truncate a tool result if it exceeds max_chars."""
    if len(result_text) <= max_chars:
        return result_text
    return result_text[: max_chars - 200] + f"\n... [truncated, {len(result_text)} total chars]"


# Tools that only read and never mutate state — safe to run concurrently.
READ_ONLY_TOOLS: set[str] = {
    # Graph queries
    "list_phenomena", "get_phenomenon", "search_graph", "get_related",
    "get_hypothesis_status", "list_assets", "find_extracted_file",
    # Sleuth Kit reads
    "partition_info", "filesystem_info", "list_directory", "find_file",
    "search_strings", "count_deleted_files", "build_filesystem_timeline",
    # Registry reads (without auto-record wrappers)
    "parse_registry_key", "search_registry", "get_user_activity",
    # Parser reads
    "read_text_file", "read_binary_preview", "search_text_file",
    "read_text_file_section", "list_extracted_dir", "parse_pcap_strings",
}


def _fix_tool_args(tool_name: str, tool_args: dict, tools: list[dict]) -> dict:
    """Try to fix misnamed tool arguments from LLM hallucination.

    The LLM sometimes confuses parameter names across tools (e.g. passing
    `key_path` to search_registry which expects `pattern`).  This function
    maps unknown kwargs to missing expected params by position/best-effort.
    """
    # Find the schema for this tool
    schema = None
    for t in tools:
        if t.get("name") == tool_name:
            schema = t.get("input_schema", {})
            break
    if schema is None:
        return tool_args

    props = schema.get("properties", {})
    required = set(schema.get("required", []))

    unknown = [k for k in tool_args if k not in props]
    if not unknown:
        return tool_args  # all args are valid, nothing to fix

    # Build the fixed args: start with valid args
    fixed = {k: v for k, v in tool_args.items() if k in props}

    # Find which expected params are still missing
    missing = [p for p in (required or props.keys()) if p not in fixed]

    # Try to map unknown args to missing params, in order
    unknown_values = [(k, tool_args[k]) for k in unknown]

    for wrong_name, value in unknown_values:
        if not missing:
            break
        # Pick the best match from missing params
        best = missing.pop(0)
        logger.warning(
            "Auto-fixing tool arg: %s(%s=...) -> %s(%s=...)",
            tool_name, wrong_name, tool_name, best,
        )
        fixed[best] = value

    return fixed


def _emit_tool_call_summary(tool_calls: list[dict], elapsed: float) -> None:
    """Emit a folded tool-call summary line for the terminal formatter.

    Instead of logging each tool call individually, we group by name:
      "list_directory x27, extract_file x3, read_text_file x3"
    """
    counts = Counter(tc.get("name", "?") for tc in tool_calls)
    parts = []
    for name, count in counts.most_common():
        if count > 1:
            parts.append(f"{name} x{count}")
        else:
            parts.append(name)
    summary = ", ".join(parts)
    logger.info(summary, extra={"event": "tool_calls", "elapsed": elapsed})


@dataclass
class _ToolBatch:
    """A batch of tool calls with the same read/write classification."""
    is_read_only: bool
    calls: list[dict] = field(default_factory=list)


def _partition_tool_calls(
    tool_calls: list[dict],
    read_only: set[str] | None = None,
) -> list[_ToolBatch]:
    """Partition tool calls into batches: consecutive read-only tools are
    grouped together (will run in parallel), write tools are isolated."""
    if read_only is None:
        read_only = READ_ONLY_TOOLS
    batches: list[_ToolBatch] = []
    for tc in tool_calls:
        is_ro = tc.get("name", "") in read_only
        if batches and batches[-1].is_read_only and is_ro:
            batches[-1].calls.append(tc)
        else:
            batches.append(_ToolBatch(is_read_only=is_ro, calls=[tc]))
    return batches


# ---------------------------------------------------------------------------
# Context compression — keeps the message list from growing unboundedly.
# ---------------------------------------------------------------------------

# Stage A: Progressive tool result decay thresholds.
# Messages are counted in (assistant, user) pairs from the END of the list.
# "Round" = one pair of (assistant tool-calling msg, user tool-result msg).
_DECAY_TIERS: list[tuple[int, int]] = [
    # (rounds_ago_threshold, max_chars_for_tool_results)
    (5,  3000),   # recent 5 rounds: keep full (3000 chars per tool result)
    (15, 500),    # 5-15 rounds ago: aggressive truncation
    (999, 100),   # older than 15 rounds: minimal stub
]


def _apply_progressive_decay(messages: list[dict]) -> list[dict]:
    """Truncate tool results in older messages to save context space.

    Operates in-place-style on a copy. Only touches user messages that
    contain <tool_result> blocks (these are the tool-result messages
    generated by tool_call_loop).
    """
    # Count rounds from the end. A "round" is a (assistant, user) pair.
    # messages alternate: [user, assistant, user, assistant, user, ...]
    # The initial user message is index 0, then pairs start at index 1.
    total = len(messages)
    if total <= 10:  # not enough messages to bother
        return messages

    result = []
    # Count tool-result user messages from the end
    tool_result_indices = [
        i for i, m in enumerate(messages)
        if m["role"] == "user" and TOOL_RESULT_TAG in m.get("content", "")
    ]

    # Build a set of indices that need decay, mapped to their max_chars
    decay_map: dict[int, int] = {}
    n_tool_msgs = len(tool_result_indices)
    for rank, idx in enumerate(reversed(tool_result_indices)):
        rounds_ago = rank  # 0 = most recent, 1 = second most recent, ...
        for threshold, max_chars in _DECAY_TIERS:
            if rounds_ago < threshold:
                decay_map[idx] = max_chars
                break

    for i, msg in enumerate(messages):
        if i in decay_map:
            max_chars = decay_map[i]
            content = msg["content"]
            if len(content) > max_chars + 200:
                # Truncate but preserve the tool_result tags structure
                truncated = content[:max_chars]
                # Count how many tool results are in this message
                n_results = content.count(TOOL_RESULT_TAG)
                truncated += (
                    f"\n... [context compressed: {len(content)} -> {max_chars} chars, "
                    f"{n_results} tool result(s)]"
                )
                result.append({"role": msg["role"], "content": truncated})
            else:
                result.append(msg)
        else:
            result.append(msg)
    return result


# Stage B: LLM-powered message folding.
# When messages exceed this count, fold the oldest ones into a summary.
_FOLD_THRESHOLD = 24      # trigger folding when messages exceed this count
_FOLD_KEEP_RECENT = 10    # always keep the most recent N messages intact
_FOLD_SUMMARY_SYSTEM = (
    "You are a concise summarizer for an ongoing forensic investigation conversation. "
    "Summarize the following early conversation between a forensic analysis agent and its "
    "tool execution results. Preserve:\n"
    "- Key findings and evidence discovered (file paths, inode numbers, timestamps)\n"
    "- Tools that were called and their important results\n"
    "- Decisions made and current investigation direction\n"
    "Keep the summary under 800 words. Use bullet points."
)


class LLMClient:
    """Calls Claude Messages API through a third-party proxy using raw httpx.

    Uses prompt-based tool calling (ReAct pattern) since the proxy does not
    support Claude's native tool_use format.
    """

    def __init__(
        self,
        base_url: str,
        api_key: str,
        model: str = "claude-sonnet-4-6",
        max_tokens: int = 4096,
        proxy: str | None = "auto",
    ) -> None:
        self.base_url = base_url.rstrip("/")
        self.api_key = api_key
        self.model = model
        self.max_tokens = max_tokens
        # proxy="auto": read from env; proxy=None/""/"none": no proxy; proxy="http://...": use it
        if proxy == "auto":
            proxy_url = os.environ.get("https_proxy") or os.environ.get("HTTPS_PROXY")
        elif proxy and proxy.lower() != "none":
            proxy_url = proxy
        else:
            proxy_url = None
        self._client = httpx.AsyncClient(
            base_url=self.base_url,
            headers={
                "x-api-key": self.api_key,
                "anthropic-version": "2023-06-01",
                "content-type": "application/json",
            },
            timeout=300.0,
            proxy=proxy_url,
        )

    async def close(self) -> None:
        await self._client.aclose()

    async def chat(
        self,
        messages: list[dict],
        system: str | None = None,
        max_retries: int = 5,
    ) -> str:
        """Send a streaming chat request and return the assembled text response.

        Uses SSE streaming to keep the connection alive and avoid gateway
        timeouts (504/524) on long-running completions.
        """
        import asyncio as _asyncio

        payload: dict[str, Any] = {
            "model": self.model,
            "max_tokens": self.max_tokens,
            "messages": messages,
            "stream": True,
        }
        if system:
            payload["system"] = system

        for attempt in range(max_retries):
            logger.debug("LLM request (stream): %d messages (attempt %d)", len(messages), attempt + 1)
            text_parts: list[str] = []
            try:
                async with self._client.stream(
                    "POST", "/v1/messages", json=payload,
                ) as resp:
                    # Check for HTTP errors before consuming stream
                    if resp.status_code >= 400:
                        body = await resp.aread()
                        raise httpx.HTTPStatusError(
                            f"Server error '{resp.status_code}' for url '{resp.url}'",
                            request=resp.request,
                            response=resp,
                        )

                    # Parse SSE events
                    async for line in resp.aiter_lines():
                        if not line.startswith("data: "):
                            continue
                        data_str = line[6:]  # strip "data: " prefix
                        if data_str.strip() == "[DONE]":
                            break
                        try:
                            event = json.loads(data_str)
                        except json.JSONDecodeError:
                            continue

                        event_type = event.get("type", "")
                        if event_type == "content_block_delta":
                            delta = event.get("delta", {})
                            if delta.get("type") == "text_delta":
                                text_parts.append(delta["text"])
                        elif event_type == "message_stop":
                            break
                        elif event_type == "error":
                            err_msg = event.get("error", {}).get("message", "Unknown streaming error")
                            raise httpx.HTTPStatusError(
                                err_msg, request=resp.request, response=resp,
                            )

                text = "".join(text_parts)
                logger.debug("LLM response (stream): %d chars", len(text))
                return text

            except (httpx.HTTPStatusError, httpx.ConnectError, httpx.ReadTimeout, httpx.RemoteProtocolError) as e:
                if attempt < max_retries - 1:
                    wait = 2 ** attempt * 10
                    logger.warning("Request failed (%s), retrying in %ds...", e, wait)
                    await _asyncio.sleep(wait)
                else:
                    raise LLMAPIError(
                        f"LLM API unreachable after {max_retries} attempts: {e}",
                        attempts=max_retries,
                    ) from e

        # Should not reach here, but just in case
        return ""

    async def tool_call_loop(
        self,
        messages: list[dict],
        tools: list[dict],
        tool_executor: dict[str, Any],
        system: str | None = None,
        max_iterations: int = 40,
    ) -> tuple[str, list[dict]]:
        """Run a ReAct-style tool-calling loop.

        The model outputs <tool_call> blocks which we parse and execute,
        feeding results back as <tool_result> blocks until the model
        outputs an <answer> block.

        Returns:
            (final_text, all_messages)
        """
        # Build system prompt with tool definitions
        tools_prompt = _build_tools_prompt(tools)
        full_system = f"{system}\n\n{tools_prompt}" if system else tools_prompt

        messages = list(messages)  # don't mutate caller's list
        _folded = False  # Track whether we've already folded once this loop

        for i in range(max_iterations):
            # ── Context compression before each API call ──────────────
            # Stage A: progressively decay old tool results
            messages = _apply_progressive_decay(messages)

            # Stage B: fold oldest messages into LLM summary if too long
            if not _folded and len(messages) > _FOLD_THRESHOLD:
                messages = await self._fold_old_messages(messages, full_system)
                _folded = True
            elif _folded and len(messages) > _FOLD_THRESHOLD + _FOLD_KEEP_RECENT:
                # Allow a second fold if messages grew back significantly
                messages = await self._fold_old_messages(messages, full_system)

            text = await self.chat(messages, system=full_system)

            # Check for final answer
            answer = _extract_answer(text)
            if answer is not None:
                messages.append({"role": "assistant", "content": text})
                return answer, messages

            # Check for tool calls
            tool_calls = _extract_tool_calls(text)

            if not tool_calls:
                # No tool calls and no answer tag — treat entire text as answer
                messages.append({"role": "assistant", "content": text})
                return text, messages

            # Execute tool calls — read-only tools run in parallel
            messages.append({"role": "assistant", "content": text})

            result_parts = []
            batches = _partition_tool_calls(tool_calls)
            t_batch_start = time.monotonic()

            for batch in batches:
                if batch.is_read_only and len(batch.calls) > 1:
                    batch_results = await self._execute_tool_batch_parallel(
                        batch.calls, tool_executor, tools,
                    )
                    result_parts.extend(batch_results)
                else:
                    for tc in batch.calls:
                        result_parts.append(
                            await self._execute_single_tool(tc, tool_executor, tools)
                        )

            # Emit folded tool-call summary for the terminal
            t_batch_elapsed = time.monotonic() - t_batch_start
            _emit_tool_call_summary(tool_calls, t_batch_elapsed)

            # Feed results back as a user message
            result_message = "\n\n".join(result_parts)
            messages.append({"role": "user", "content": result_message})

        logger.warning("Tool call loop hit max iterations (%d)", max_iterations)
        return "[Max tool call iterations reached]", messages

    async def _execute_single_tool(
        self, tc: dict, tool_executor: dict[str, Any],
        tools: list[dict] | None = None,
    ) -> str:
        """Execute a single tool call and return the formatted result."""
        tool_name = tc.get("name", "")
        tool_args = tc.get("arguments", {})

        if tools:
            tool_args = _fix_tool_args(tool_name, tool_args, tools)

        logger.info("Calling tool: %s(%s)", tool_name, json.dumps(tool_args, ensure_ascii=False))

        executor = tool_executor.get(tool_name)
        if executor is None:
            result_text = f"Error: unknown tool '{tool_name}'"
        else:
            try:
                result_text = await executor(**tool_args)
            except Exception as e:
                logger.error("Tool %s failed: %s", tool_name, e)
                result_text = f"Error executing {tool_name}: {e}"

        return (
            f"{TOOL_RESULT_TAG}\n"
            f"[{tool_name}] {_truncate_tool_result(result_text)}\n"
            f"{TOOL_RESULT_END}"
        )

    async def _execute_tool_batch_parallel(
        self, calls: list[dict], tool_executor: dict[str, Any],
        tools: list[dict] | None = None,
    ) -> list[str]:
        """Execute multiple read-only tool calls concurrently."""
        logger.info("Executing %d read-only tools in parallel", len(calls))

        async def _run_one(tc: dict) -> str:
            tool_name = tc.get("name", "")
            tool_args = tc.get("arguments", {})
            if tools:
                tool_args = _fix_tool_args(tool_name, tool_args, tools)
            logger.info("Calling tool (parallel): %s(%s)", tool_name, json.dumps(tool_args, ensure_ascii=False))
            executor = tool_executor.get(tool_name)
            if executor is None:
                result_text = f"Error: unknown tool '{tool_name}'"
            else:
                try:
                    result_text = await executor(**tool_args)
                except Exception as e:
                    logger.error("Tool %s failed: %s", tool_name, e)
                    result_text = f"Error executing {tool_name}: {e}"
            return (
                f"{TOOL_RESULT_TAG}\n"
                f"[{tool_name}] {_truncate_tool_result(result_text)}\n"
                f"{TOOL_RESULT_END}"
            )

        results = await asyncio.gather(*[_run_one(tc) for tc in calls])
        return list(results)

    async def _fold_old_messages(
        self, messages: list[dict], system: str,
    ) -> list[dict]:
        """Fold old messages into an LLM-generated summary (Stage B).

        Keeps the most recent _FOLD_KEEP_RECENT messages intact and
        replaces earlier ones with a single summary message.
        """
        n_to_fold = len(messages) - _FOLD_KEEP_RECENT
        if n_to_fold <= 2:
            return messages

        old_messages = messages[:n_to_fold]
        recent_messages = messages[n_to_fold:]

        # Build a text dump of old messages for summarization
        old_text_parts = []
        for msg in old_messages:
            role = msg["role"]
            content = msg.get("content", "")
            # Truncate each message for the summary prompt to avoid overload
            if len(content) > 1000:
                content = content[:1000] + "..."
            old_text_parts.append(f"[{role}]: {content}")
        old_text = "\n\n".join(old_text_parts)

        # Cap total size sent to summarizer
        if len(old_text) > 15000:
            old_text = old_text[:15000] + "\n\n... [further messages omitted for brevity]"

        logger.info(
            "Context folding: summarizing %d old messages (%d chars) into summary",
            n_to_fold, len(old_text),
        )

        try:
            summary = await self.chat(
                messages=[{"role": "user", "content": old_text}],
                system=_FOLD_SUMMARY_SYSTEM,
            )
        except Exception as e:
            logger.warning("Context folding failed: %s — keeping original messages", e)
            return messages

        # Replace old messages with a single summary
        summary_message = {
            "role": "user",
            "content": (
                f"[Context summary — the following summarizes {n_to_fold} earlier "
                f"messages in this conversation]\n\n{summary}"
            ),
        }
        return [summary_message] + recent_messages