from __future__ import annotations

import re
from pathlib import Path
from typing import Any

from langchain_core.messages import HumanMessage, SystemMessage
from langgraph.graph import END, StateGraph

from gaia_agent.answer import normalize_answer
from gaia_agent.config import settings
from gaia_agent.llms import create_chat_model
from gaia_agent.observability import traced_step
from gaia_agent.prompts import (
    GAIA_AGENT_SYSTEM_PROMPT,
    GAIA_QUERY_PROMPT,
    GAIA_VERIFY_PROMPT,
)
from gaia_agent.state import GaiaState
from gaia_agent.tools.files import (
    download_task_file,
    read_text_file,
    summarize_spreadsheet,
)
from gaia_agent.tools.media import image_data_url, transcribe_audio_file
from gaia_agent.tools.python_repl import run_python_file
from gaia_agent.tools.web import (
    extract_urls,
    fetch_url,
    get_youtube_transcript,
    web_search,
)


MAX_EVIDENCE_CHARS = 36_000
MAX_WEB_PAGES = 4


def build_graph(trace=None, llm=None):
    graph = StateGraph(GaiaState)
    chat_model = llm or create_chat_model()

    def ingest_task(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            evidence = list(state.get("evidence", []))
            output: dict[str, Any] = {
                "evidence": evidence,
                "tool_outputs": list(state.get("tool_outputs", [])),
            }
            if state.get("file_path") or not state.get("file_name"):
                return output

            try:
                path = download_task_file(
                    settings.gaia_api_url,
                    state["task_id"],
                    state.get("file_name"),
                )
                output["file_path"] = str(path)
                evidence.append(f"Downloaded attached file to {path}.")
            except Exception as exc:
                evidence.append(f"Could not download attached file: {exc}")
                output["error"] = str(exc)
            return output

        return traced_step(trace, "ingest_task", run)

    def classify_task(state: GaiaState) -> dict[str, str]:
        def run() -> dict[str, str]:
            question = state["question"].lower()
            file_name = state.get("file_name", "").lower()

            if file_name.endswith((".xlsx", ".xls", ".csv")):
                task_type = "spreadsheet"
            elif file_name.endswith(".py"):
                task_type = "python_file"
            elif file_name.endswith((".mp3", ".wav", ".m4a", ".ogg", ".flac")):
                task_type = "audio"
            elif file_name.endswith((".png", ".jpg", ".jpeg", ".webp")):
                task_type = "image"
            elif "youtube.com" in question or "youtu.be" in question:
                task_type = "youtube"
            elif _looks_like_computation(question):
                task_type = "compute"
            elif _looks_like_direct(question):
                task_type = "direct"
            else:
                task_type = "web"
            return {"task_type": task_type}

        return traced_step(trace, "classify_task", run)

    def solve_direct(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            answer = _invoke_text(
                chat_model,
                GAIA_AGENT_SYSTEM_PROMPT,
                f"Question:\n{state['question']}",
            )
            return {"draft_answer": answer}

        return traced_step(trace, "solve_direct", run)

    def solve_compute(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            answer = _invoke_text(
                chat_model,
                GAIA_AGENT_SYSTEM_PROMPT,
                (
                    "Solve this question carefully. If it includes a table or "
                    "formal rule, compute the requested value exactly.\n\n"
                    f"Question:\n{state['question']}"
                ),
            )
            return {"draft_answer": answer}

        return traced_step(trace, "solve_compute", run)

    def solve_spreadsheet(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            evidence = list(state.get("evidence", []))
            path = state.get("file_path")
            if not path:
                evidence.append("Attached spreadsheet is unavailable.")
                answer = _invoke_text(
                    chat_model,
                    GAIA_AGENT_SYSTEM_PROMPT,
                    _question_with_evidence(state["question"], evidence),
                )
                return {"evidence": evidence, "draft_answer": answer}

            summary = summarize_spreadsheet(path)
            evidence.append(f"Spreadsheet summary:\n{summary}")
            answer = _invoke_text(
                chat_model,
                GAIA_AGENT_SYSTEM_PROMPT,
                _question_with_evidence(state["question"], evidence),
            )
            return {"evidence": evidence, "draft_answer": answer}

        return traced_step(trace, "solve_spreadsheet", run)

    def solve_python_file(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            evidence = list(state.get("evidence", []))
            path = state.get("file_path")
            if not path:
                evidence.append("Attached Python file is unavailable.")
                answer = _invoke_text(
                    chat_model,
                    GAIA_AGENT_SYSTEM_PROMPT,
                    _question_with_evidence(state["question"], evidence),
                )
                return {"evidence": evidence, "draft_answer": answer}

            source = read_text_file(path, max_chars=30_000)
            result = run_python_file(path)
            evidence.append(f"Attached Python source:\n{source}")
            evidence.append(
                "Python execution result:\n"
                f"exit_code={result['exit_code']}\n"
                f"stdout:\n{result['stdout']}\n"
                f"stderr:\n{result['stderr']}"
            )

            stdout = str(result.get("stdout", "")).strip()
            if stdout and not str(result.get("stderr", "")).strip():
                draft = stdout.splitlines()[-1]
                verified = draft
            else:
                draft = _invoke_text(
                    chat_model,
                    GAIA_AGENT_SYSTEM_PROMPT,
                    _question_with_evidence(state["question"], evidence),
                )
                verified = ""
            output = {"evidence": evidence, "draft_answer": draft}
            if verified:
                output["verified_answer"] = verified
            return output

        return traced_step(trace, "solve_python_file", run)

    def solve_audio(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            evidence = list(state.get("evidence", []))
            path = state.get("file_path")
            if not path:
                evidence.append("Attached audio file is unavailable.")
            else:
                try:
                    transcript = transcribe_audio_file(path)
                    evidence.append(f"Audio transcript:\n{transcript}")
                except Exception as exc:
                    evidence.append(f"Audio transcription failed: {exc}")

            answer = _invoke_text(
                chat_model,
                GAIA_AGENT_SYSTEM_PROMPT,
                _question_with_evidence(state["question"], evidence),
            )
            return {"evidence": evidence, "draft_answer": answer}

        return traced_step(trace, "solve_audio", run)

    def solve_image(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            evidence = list(state.get("evidence", []))
            path = state.get("file_path")
            if path:
                try:
                    answer = _invoke_image(chat_model, state["question"], path)
                    evidence.append(f"Image analyzed from {path}.")
                except Exception as exc:
                    evidence.append(f"Image analysis failed: {exc}")
                    answer = _invoke_text(
                        chat_model,
                        GAIA_AGENT_SYSTEM_PROMPT,
                        _question_with_evidence(state["question"], evidence),
                    )
            else:
                evidence.append("Attached image file is unavailable.")
                answer = _invoke_text(
                    chat_model,
                    GAIA_AGENT_SYSTEM_PROMPT,
                    _question_with_evidence(state["question"], evidence),
                )
            return {"evidence": evidence, "draft_answer": answer}

        return traced_step(trace, "solve_image", run)

    def solve_youtube(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            evidence = list(state.get("evidence", []))
            urls = extract_urls(state["question"])
            for url in urls:
                if "youtube.com" not in url and "youtu.be" not in url:
                    continue
                try:
                    transcript = get_youtube_transcript(url)
                    evidence.append(f"YouTube transcript for {url}:\n{transcript}")
                except Exception as exc:
                    evidence.append(f"YouTube transcript failed for {url}: {exc}")

            answer = _invoke_text(
                chat_model,
                GAIA_AGENT_SYSTEM_PROMPT,
                _question_with_evidence(state["question"], evidence),
            )
            return {"evidence": evidence, "draft_answer": answer}

        return traced_step(trace, "solve_youtube", run)

    def solve_web(state: GaiaState) -> dict[str, Any]:
        def run() -> dict[str, Any]:
            evidence = list(state.get("evidence", []))
            queries = _build_search_queries(chat_model, state["question"])
            seen_urls: set[str] = set()

            for query in queries:
                try:
                    results = web_search(query, max_results=5)
                except Exception as exc:
                    evidence.append(f"Search failed for {query!r}: {exc}")
                    continue

                if results:
                    evidence.append(
                        "Search results for "
                        f"{query!r}:\n"
                        + "\n".join(f"- {item.title}: {item.url}" for item in results)
                    )

                for result in results:
                    if len(seen_urls) >= MAX_WEB_PAGES:
                        break
                    if result.url in seen_urls:
                        continue
                    seen_urls.add(result.url)
                    try:
                        page_text = fetch_url(result.url, max_chars=12_000)
                    except Exception as exc:
                        evidence.append(f"Fetch failed for {result.url}: {exc}")
                        continue
                    evidence.append(f"Page: {result.title}\nURL: {result.url}\n{page_text}")

            answer = _invoke_text(
                chat_model,
                GAIA_AGENT_SYSTEM_PROMPT,
                _question_with_evidence(state["question"], evidence),
            )
            return {"evidence": evidence, "draft_answer": answer}

        return traced_step(trace, "solve_web", run)

    def verify_answer(state: GaiaState) -> dict[str, str]:
        def run() -> dict[str, str]:
            if state.get("verified_answer"):
                return {"verified_answer": state["verified_answer"]}

            evidence = _trim_evidence(state.get("evidence", []))
            verified = _invoke_text(
                chat_model,
                GAIA_VERIFY_PROMPT,
                (
                    f"Question:\n{state['question']}\n\n"
                    f"Evidence:\n{evidence}\n\n"
                    f"Draft answer:\n{state.get('draft_answer', '')}"
                ),
            )
            return {"verified_answer": verified}

        return traced_step(trace, "verify_answer", run)

    def normalize_final_answer(state: GaiaState) -> dict[str, str]:
        def run() -> dict[str, str]:
            answer = state.get("verified_answer") or state.get("draft_answer", "")
            return {"final_answer": normalize_answer(answer)}

        return traced_step(trace, "normalize_final_answer", run)

    graph.add_node("ingest_task", ingest_task)
    graph.add_node("classify_task", classify_task)
    graph.add_node("solve_direct", solve_direct)
    graph.add_node("solve_compute", solve_compute)
    graph.add_node("solve_spreadsheet", solve_spreadsheet)
    graph.add_node("solve_python_file", solve_python_file)
    graph.add_node("solve_audio", solve_audio)
    graph.add_node("solve_image", solve_image)
    graph.add_node("solve_youtube", solve_youtube)
    graph.add_node("solve_web", solve_web)
    graph.add_node("verify_answer", verify_answer)
    graph.add_node("normalize_final_answer", normalize_final_answer)

    graph.set_entry_point("ingest_task")
    graph.add_edge("ingest_task", "classify_task")
    graph.add_conditional_edges(
        "classify_task",
        lambda state: state.get("task_type", "web"),
        {
            "direct": "solve_direct",
            "compute": "solve_compute",
            "spreadsheet": "solve_spreadsheet",
            "python_file": "solve_python_file",
            "audio": "solve_audio",
            "image": "solve_image",
            "youtube": "solve_youtube",
            "web": "solve_web",
        },
    )
    for node in (
        "solve_direct",
        "solve_compute",
        "solve_spreadsheet",
        "solve_python_file",
        "solve_audio",
        "solve_image",
        "solve_youtube",
        "solve_web",
    ):
        graph.add_edge(node, "verify_answer")
    graph.add_edge("verify_answer", "normalize_final_answer")
    graph.add_edge("normalize_final_answer", END)

    return graph.compile()


def _invoke_text(chat_model, system_prompt: str, user_prompt: str) -> str:
    response = chat_model.invoke(
        [
            ("system", system_prompt),
            ("user", user_prompt),
        ]
    )
    return str(response.content)


def _invoke_image(chat_model, question: str, path: str | Path) -> str:
    response = chat_model.invoke(
        [
            SystemMessage(content=GAIA_AGENT_SYSTEM_PROMPT),
            HumanMessage(
                content=[
                    {"type": "text", "text": question},
                    {
                        "type": "image_url",
                        "image_url": {"url": image_data_url(path)},
                    },
                ]
            ),
        ]
    )
    return str(response.content)


def _build_search_queries(chat_model, question: str) -> list[str]:
    raw_queries = _invoke_text(
        chat_model,
        GAIA_QUERY_PROMPT,
        f"Question:\n{question}",
    )
    queries = [
        re.sub(r"^\s*[-*\d.)]+\s*", "", line).strip()
        for line in raw_queries.splitlines()
        if line.strip()
    ]
    queries = [query.strip("\"'") for query in queries if len(query.strip("\"'")) > 3]
    if question not in queries:
        queries.append(question)
    return queries[:3]


def _question_with_evidence(question: str, evidence: list[str]) -> str:
    return f"Question:\n{question}\n\nEvidence:\n{_trim_evidence(evidence)}"


def _trim_evidence(evidence: list[str]) -> str:
    text = "\n\n---\n\n".join(evidence)
    if len(text) <= MAX_EVIDENCE_CHARS:
        return text
    return f"{text[:MAX_EVIDENCE_CHARS]}\n\n[trimmed after {MAX_EVIDENCE_CHARS} chars]"


def _looks_like_computation(question: str) -> bool:
    markers = (
        "given this table",
        "provide the subset",
        "counter-examples",
        "not commutative",
        "calculate",
        "numeric output",
    )
    return any(marker in question for marker in markers)


def _looks_like_direct(question: str) -> bool:
    if question.count(" ") <= 8:
        return True
    if _looks_reversed(question):
        return True
    direct_markers = (
        "grocery list",
        "categorizing things",
        "write the opposite",
    )
    return any(marker in question for marker in direct_markers)


def _looks_reversed(question: str) -> bool:
    words = re.findall(r"[a-z]{4,}", question)
    if len(words) < 3:
        return False
    reversed_common = {"rewsna", "drow", "etirw", "ecnetnes", "dnatsrednu"}
    return len(reversed_common.intersection(words)) >= 2