marchwarden/researchers/web/agent.py

"""Web researcher agent — the inner agentic loop.

Takes a question, runs a plan→search→fetch→iterate→synthesize loop
using Claude as the reasoning engine and Tavily/httpx as tools.
Returns a ResearchResult conforming to the v1 contract.
"""

import asyncio
import json
import time
from typing import Optional

import structlog
from anthropic import Anthropic

from obs import get_logger
from obs.costs import CostLedger
from researchers.web.models import (
    Citation,
    ConfidenceFactors,
    CostMetadata,
    DiscoveryEvent,
    Gap,
    GapCategory,
    OpenQuestion,
    ResearchConstraints,
    ResearchResult,
    constraints_for_depth,
)
from researchers.web.tools import SearchResult, fetch_url, tavily_search
from researchers.web.trace import TraceLogger

log = get_logger("marchwarden.researcher.web")

SYSTEM_PROMPT = """\
You are a Marchwarden — a research specialist stationed at the frontier of knowledge. \
Your job is to investigate a question thoroughly using web search and URL fetching, \
then produce a grounded, evidence-based answer.

## Your process

1. **Plan**: Decide what to search for. Break complex questions into sub-queries.
2. **Search**: Use the web_search tool to find relevant sources.
3. **Fetch**: Use the fetch_url tool to get full content from promising URLs.
4. **Iterate**: If you don't have enough evidence, search again with refined queries.
5. **Stop**: When you have sufficient evidence OR you've exhausted your budget.

## Rules

- Every claim must be traceable to a source you actually fetched.
- If you can't find information, say so — never fabricate.
- If sources contradict each other, note the contradiction.
- If the question requires expertise outside web search (academic papers, databases, \
legal documents), note it as a discovery for another researcher.
- Be efficient. Don't fetch URLs that are clearly irrelevant from their title/snippet.
- Prefer authoritative sources (.gov, .edu, established organizations) over blogs/forums.
"""

SYNTHESIS_PROMPT = """\
Based on the evidence gathered, produce a structured research result as JSON.

## Evidence gathered
{evidence}

## Original question
{question}

## Context from caller
{context}

## Instructions

Produce a JSON object with these exact fields:

{{
  "answer": "Your synthesized answer. Every claim must trace to a citation.",
  "citations": [
    {{
      "source": "web",
      "locator": "the exact URL",
      "title": "page title",
      "snippet": "your 50-200 char summary of why this source is relevant",
      "raw_excerpt": "verbatim 100-500 char excerpt from the source that supports your claim",
      "confidence": 0.0-1.0
    }}
  ],
  "gaps": [
    {{
      "topic": "what wasn't resolved",
      "category": "source_not_found|access_denied|budget_exhausted|contradictory_sources|scope_exceeded",
      "detail": "human-readable explanation"
    }}
  ],
  "discovery_events": [
    {{
      "type": "related_research|new_source|contradiction",
      "suggested_researcher": "arxiv|database|legal|null",
      "query": "suggested query for that researcher",
      "reason": "why this matters",
      "source_locator": "URL where you found this, or null"
    }}
  ],
  "open_questions": [
    {{
      "question": "A follow-up question that emerged from the research",
      "context": "What evidence prompted this question",
      "priority": "high|medium|low",
      "source_locator": "URL where this question arose, or null"
    }}
  ],
  "confidence": 0.0-1.0,
  "confidence_factors": {{
    "num_corroborating_sources": 0,
    "source_authority": "high|medium|low",
    "contradiction_detected": false,
    "query_specificity_match": 0.0-1.0,
    "budget_exhausted": false,
    "recency": "current|recent|dated|null"
  }}
}}

Respond with ONLY the JSON object, no markdown fences, no explanation.
"""

# Tool definitions for Claude's tool_use API
TOOLS = [
    {
        "name": "web_search",
        "description": (
            "Search the web for information. Returns titles, URLs, snippets, "
            "and sometimes full page content. Use this to find sources."
        ),
        "input_schema": {
            "type": "object",
            "properties": {
                "query": {
                    "type": "string",
                    "description": "The search query.",
                },
                "max_results": {
                    "type": "integer",
                    "description": "Number of results (1-10). Default 5.",
                    "default": 5,
                },
            },
            "required": ["query"],
        },
    },
    {
        "name": "fetch_url",
        "description": (
            "Fetch the full text content of a URL. Use this when a search result "
            "looks promising but the snippet isn't enough. Returns extracted text."
        ),
        "input_schema": {
            "type": "object",
            "properties": {
                "url": {
                    "type": "string",
                    "description": "The URL to fetch.",
                },
            },
            "required": ["url"],
        },
    },
]


class WebResearcher:
    """Agentic web researcher that searches, fetches, and synthesizes."""

    def __init__(
        self,
        anthropic_api_key: str,
        tavily_api_key: str,
        model_id: str = "claude-sonnet-4-6",
        trace_dir: Optional[str] = None,
        cost_ledger: Optional[CostLedger] = None,
    ):
        self.client = Anthropic(api_key=anthropic_api_key)
        self.tavily_api_key = tavily_api_key
        self.model_id = model_id
        self.trace_dir = trace_dir
        # Lazy default — only constructed if no override is given. Tests
        # inject a CostLedger pointed at a tmp path to avoid touching
        # the real ledger file.
        self.cost_ledger = cost_ledger

    async def research(
        self,
        question: str,
        context: Optional[str] = None,
        depth: str = "balanced",
        constraints: Optional[ResearchConstraints] = None,
    ) -> ResearchResult:
        """Run a full research loop on a question.

        Args:
            question: The question to investigate.
            context: What the caller already knows (optional).
            depth: "shallow", "balanced", or "deep".
            constraints: Budget and iteration limits.

        Returns:
            A ResearchResult conforming to the v1 contract.
        """
        # If the caller didn't supply explicit constraints, build them
        # from the depth preset (Issue #30). Callers that DO pass a
        # ResearchConstraints are taken at their word — explicit wins.
        constraints = constraints or constraints_for_depth(depth)
        trace = TraceLogger(trace_dir=self.trace_dir)
        start_time = time.time()
        total_tokens = 0
        tokens_input = 0
        tokens_output = 0
        iterations = 0
        evidence: list[dict] = []
        budget_exhausted = False
        tavily_searches = 0

        # Bind trace context so every downstream log call automatically
        # carries trace_id and researcher. Cleared in the finally block.
        structlog.contextvars.bind_contextvars(
            trace_id=trace.trace_id,
            researcher="web",
        )
        log.info(
            "research_started",
            question=question,
            depth=depth,
            max_iterations=constraints.max_iterations,
            token_budget=constraints.token_budget,
            model_id=self.model_id,
        )

        trace.log_step(
            "start",
            decision=f"Beginning research: depth={depth}",
            question=question,
            context=context or "",
            max_iterations=constraints.max_iterations,
            token_budget=constraints.token_budget,
        )

        # Build initial message
        user_message = f"Research this question: {question}"
        if context:
            user_message += f"\n\nContext from the caller: {context}"
        user_message += f"\n\nResearch depth: {depth}"

        messages = [{"role": "user", "content": user_message}]

        # --- Tool-use loop ---
        # Budget policy: the loop honors token_budget as a soft cap. Before
        # starting a new iteration we check whether we've already hit the
        # budget; if so we stop and let synthesis run on whatever evidence
        # we already have. Synthesis tokens are tracked but not capped here
        # — the synthesis call is always allowed to complete so the caller
        # gets a structured result rather than a stub.
        while iterations < constraints.max_iterations:
            if total_tokens >= constraints.token_budget:
                budget_exhausted = True
                trace.log_step(
                    "budget_exhausted",
                    decision=(
                        f"Token budget reached before iteration "
                        f"{iterations + 1}: {total_tokens}/{constraints.token_budget}"
                    ),
                )
                break

            iterations += 1

            trace.log_step(
                "iteration_start",
                decision=f"Starting iteration {iterations}/{constraints.max_iterations}",
                tokens_so_far=total_tokens,
            )

            response = self.client.messages.create(
                model=self.model_id,
                max_tokens=4096,
                system=SYSTEM_PROMPT,
                messages=messages,
                tools=TOOLS,
            )

            # Track tokens
            tokens_input += response.usage.input_tokens
            tokens_output += response.usage.output_tokens
            total_tokens += response.usage.input_tokens + response.usage.output_tokens

            # Check if the model wants to use tools
            tool_calls = [b for b in response.content if b.type == "tool_use"]
            tavily_searches += sum(
                1 for tc in tool_calls if tc.name == "web_search"
            )

            if not tool_calls:
                # Model is done researching — extract any final text
                text_blocks = [b.text for b in response.content if b.type == "text"]
                if text_blocks:
                    trace.log_step(
                        "agent_message",
                        decision="Agent finished tool use",
                        message=text_blocks[0][:500],
                    )
                break

            # Process each tool call
            tool_results = []
            for tool_call in tool_calls:
                result_content = await self._execute_tool(
                    tool_call.name,
                    tool_call.input,
                    evidence,
                    trace,
                    constraints,
                )
                tool_results.append(
                    {
                        "type": "tool_result",
                        "tool_use_id": tool_call.id,
                        "content": result_content,
                    }
                )

            # Append assistant response + tool results to conversation
            messages.append({"role": "assistant", "content": response.content})
            messages.append({"role": "user", "content": tool_results})

        # --- Synthesis step ---
        trace.log_step(
            "synthesis_start",
            decision="Beginning synthesis of gathered evidence",
            evidence_count=len(evidence),
            iterations_run=iterations,
            tokens_used=total_tokens,
        )

        result, synth_in, synth_out = await self._synthesize(
            question=question,
            context=context,
            evidence=evidence,
            trace=trace,
            total_tokens=total_tokens,
            iterations=iterations,
            start_time=start_time,
            budget_exhausted=budget_exhausted,
        )
        tokens_input += synth_in
        tokens_output += synth_out

        trace.log_step(
            "complete",
            decision="Research complete",
            confidence=result.confidence,
            citation_count=len(result.citations),
            gap_count=len(result.gaps),
            discovery_count=len(result.discovery_events),
        )
        trace.close()

        log.info(
            "research_completed",
            confidence=result.confidence,
            citations=len(result.citations),
            gaps=len(result.gaps),
            discovery_events=len(result.discovery_events),
            tokens_used=result.cost_metadata.tokens_used,
            iterations_run=result.cost_metadata.iterations_run,
            wall_time_sec=result.cost_metadata.wall_time_sec,
            budget_exhausted=result.cost_metadata.budget_exhausted,
        )

        # Append to the operational cost ledger. Construct on first use
        # so test injection (cost_ledger=...) and the env override
        # (MARCHWARDEN_COST_LEDGER) both work without forcing every
        # caller to build a CostLedger explicitly.
        try:
            ledger = self.cost_ledger or CostLedger()
            ledger.record(
                trace_id=result.trace_id,
                question=question,
                model_id=self.model_id,
                tokens_used=result.cost_metadata.tokens_used,
                tokens_input=tokens_input,
                tokens_output=tokens_output,
                iterations_run=result.cost_metadata.iterations_run,
                wall_time_sec=result.cost_metadata.wall_time_sec,
                tavily_searches=tavily_searches,
                budget_exhausted=result.cost_metadata.budget_exhausted,
                confidence=result.confidence,
            )
        except Exception as ledger_err:
            # Never let a ledger failure poison a successful research call.
            log.warning("cost_ledger_write_failed", error=str(ledger_err))

        structlog.contextvars.clear_contextvars()

        return result

    async def _execute_tool(
        self,
        tool_name: str,
        tool_input: dict,
        evidence: list[dict],
        trace: TraceLogger,
        constraints: ResearchConstraints,
    ) -> str:
        """Execute a tool call and return the result as a string."""

        if tool_name == "web_search":
            query = tool_input.get("query", "")
            max_results = min(
                tool_input.get("max_results", 5),
                constraints.max_sources,
            )

            trace.log_step(
                "web_search",
                decision=f"Searching: {query}",
                query=query,
                max_results=max_results,
            )

            results = tavily_search(
                api_key=self.tavily_api_key,
                query=query,
                max_results=max_results,
            )

            # Store evidence
            for r in results:
                ev = {
                    "type": "search_result",
                    "url": r.url,
                    "title": r.title,
                    "content": r.content,
                    "raw_content": r.raw_content,
                    "content_hash": r.content_hash,
                    "score": r.score,
                }
                evidence.append(ev)

            trace.log_step(
                "web_search_complete",
                decision=f"Got {len(results)} results",
                result_count=len(results),
                urls=[r.url for r in results],
            )

            # Return results as text for the LLM
            return _format_search_results(results)

        elif tool_name == "fetch_url":
            url = tool_input.get("url", "")

            trace.log_step(
                "fetch_url",
                decision=f"Fetching: {url}",
                url=url,
            )

            result = await fetch_url(url)

            trace.log_step(
                "fetch_url_complete",
                decision="Fetch succeeded" if result.success else f"Fetch failed: {result.error}",
                url=url,
                content_hash=result.content_hash,
                content_length=result.content_length,
                success=result.success,
            )

            if result.success:
                # Store evidence
                evidence.append(
                    {
                        "type": "fetched_page",
                        "url": url,
                        "content": result.text[:10000],
                        "content_hash": result.content_hash,
                        "content_length": result.content_length,
                    }
                )
                # Return truncated text for the LLM
                return result.text[:8000]
            else:
                return f"Failed to fetch URL: {result.error}"

        return f"Unknown tool: {tool_name}"

    async def _synthesize(
        self,
        question: str,
        context: Optional[str],
        evidence: list[dict],
        trace: TraceLogger,
        total_tokens: int,
        iterations: int,
        start_time: float,
        budget_exhausted: bool,
    ) -> tuple[ResearchResult, int, int]:
        """Ask the LLM to synthesize evidence into a ResearchResult.

        Returns ``(result, synthesis_input_tokens, synthesis_output_tokens)``
        so the caller can track per-call token splits for cost estimation.
        """

        # Format evidence for the synthesis prompt
        evidence_text = ""
        for i, ev in enumerate(evidence, 1):
            if ev["type"] == "search_result":
                content = ev.get("raw_content") or ev.get("content", "")
                evidence_text += (
                    f"\n--- Source {i} (search result) ---\n"
                    f"URL: {ev['url']}\n"
                    f"Title: {ev['title']}\n"
                    f"Content hash: {ev['content_hash']}\n"
                    f"Content: {content[:3000]}\n"
                )
            elif ev["type"] == "fetched_page":
                evidence_text += (
                    f"\n--- Source {i} (fetched page) ---\n"
                    f"URL: {ev['url']}\n"
                    f"Content hash: {ev['content_hash']}\n"
                    f"Content: {ev['content'][:3000]}\n"
                )

        prompt = SYNTHESIS_PROMPT.format(
            evidence=evidence_text or "(No evidence gathered)",
            question=question,
            context=context or "(No additional context)",
        )

        response = self.client.messages.create(
            model=self.model_id,
            max_tokens=16384,
            messages=[{"role": "user", "content": prompt}],
        )

        synth_in = response.usage.input_tokens
        synth_out = response.usage.output_tokens
        total_tokens += synth_in + synth_out
        wall_time = time.time() - start_time

        # Parse the JSON response
        raw_text = response.content[0].text.strip()
        stop_reason = response.stop_reason
        # Strip markdown fences if the model added them despite instructions
        if raw_text.startswith("```"):
            raw_text = raw_text.split("\n", 1)[1] if "\n" in raw_text else raw_text[3:]
        if raw_text.endswith("```"):
            raw_text = raw_text[:-3].strip()

        try:
            data = json.loads(raw_text)
        except json.JSONDecodeError as parse_err:
            trace.log_step(
                "synthesis_error",
                decision=(
                    f"Failed to parse synthesis JSON ({parse_err}); "
                    f"stop_reason={stop_reason}"
                ),
                stop_reason=stop_reason,
                parse_error=str(parse_err),
                raw_response=raw_text,
            )
            return (
                self._fallback_result(
                    question, evidence, trace, total_tokens, iterations,
                    wall_time, budget_exhausted,
                ),
                synth_in,
                synth_out,
            )

        trace.log_step(
            "synthesis_complete",
            decision="Parsed synthesis JSON successfully",
        )

        # Build the ResearchResult from parsed JSON
        try:
            citations = [
                Citation(
                    source=c.get("source", "web"),
                    locator=c.get("locator", ""),
                    title=c.get("title"),
                    snippet=c.get("snippet"),
                    raw_excerpt=c.get("raw_excerpt", ""),
                    confidence=c.get("confidence", 0.5),
                )
                for c in data.get("citations", [])
            ]

            gaps = [
                Gap(
                    topic=g.get("topic", ""),
                    category=GapCategory(g.get("category", "source_not_found")),
                    detail=g.get("detail", ""),
                )
                for g in data.get("gaps", [])
            ]

            discovery_events = [
                DiscoveryEvent(
                    type=d.get("type", "related_research"),
                    suggested_researcher=d.get("suggested_researcher"),
                    query=d.get("query", ""),
                    reason=d.get("reason", ""),
                    source_locator=d.get("source_locator"),
                )
                for d in data.get("discovery_events", [])
            ]

            open_questions = [
                OpenQuestion(
                    question=q.get("question", ""),
                    context=q.get("context", ""),
                    priority=q.get("priority", "medium"),
                    source_locator=q.get("source_locator"),
                )
                for q in data.get("open_questions", [])
            ]

            cf = data.get("confidence_factors", {})
            confidence_factors = ConfidenceFactors(
                num_corroborating_sources=cf.get("num_corroborating_sources", 0),
                source_authority=cf.get("source_authority", "low"),
                contradiction_detected=cf.get("contradiction_detected", False),
                query_specificity_match=cf.get("query_specificity_match", 0.5),
                budget_exhausted=budget_exhausted or cf.get("budget_exhausted", False),
                recency=cf.get("recency"),
            )

            return (
                ResearchResult(
                    answer=data.get("answer", "No answer could be synthesized."),
                    citations=citations,
                    gaps=gaps,
                    discovery_events=discovery_events,
                    open_questions=open_questions,
                    confidence=data.get("confidence", 0.5),
                    confidence_factors=confidence_factors,
                    cost_metadata=CostMetadata(
                        tokens_used=total_tokens,
                        iterations_run=iterations,
                        wall_time_sec=wall_time,
                        budget_exhausted=budget_exhausted,
                        model_id=self.model_id,
                    ),
                    trace_id=trace.trace_id,
                ),
                synth_in,
                synth_out,
            )
        except Exception as e:
            trace.log_step(
                "synthesis_build_error",
                decision=f"Failed to build ResearchResult: {e}",
            )
            return (
                self._fallback_result(
                    question, evidence, trace, total_tokens, iterations,
                    wall_time, budget_exhausted,
                ),
                synth_in,
                synth_out,
            )

    def _fallback_result(
        self,
        question: str,
        evidence: list[dict],
        trace: TraceLogger,
        total_tokens: int,
        iterations: int,
        wall_time: float,
        budget_exhausted: bool,
    ) -> ResearchResult:
        """Produce a minimal valid ResearchResult when synthesis fails."""
        return ResearchResult(
            answer=f"Research on '{question}' completed but synthesis failed. {len(evidence)} sources were gathered.",
            citations=[],
            gaps=[
                Gap(
                    topic="synthesis",
                    category=GapCategory.BUDGET_EXHAUSTED
                    if budget_exhausted
                    else GapCategory.SOURCE_NOT_FOUND,
                    detail="The synthesis step failed to produce structured output.",
                )
            ],
            discovery_events=[],
            confidence=0.1,
            confidence_factors=ConfidenceFactors(
                num_corroborating_sources=0,
                source_authority="low",
                contradiction_detected=False,
                query_specificity_match=0.0,
                budget_exhausted=budget_exhausted,
                recency=None,
            ),
            cost_metadata=CostMetadata(
                tokens_used=total_tokens,
                iterations_run=iterations,
                wall_time_sec=wall_time,
                budget_exhausted=budget_exhausted,
                model_id=self.model_id,
            ),
            trace_id=trace.trace_id,
        )


def _format_search_results(results: list[SearchResult]) -> str:
    """Format search results as readable text for the LLM."""
    parts = []
    for i, r in enumerate(results, 1):
        content = r.raw_content or r.content
        parts.append(
            f"Result {i}:\n"
            f"  Title: {r.title}\n"
            f"  URL: {r.url}\n"
            f"  Relevance: {r.score:.2f}\n"
            f"  Content: {content[:2000]}\n"
        )
    return "\n".join(parts) if parts else "No results found."