import os
import re
import base64
import json
from typing import Any, Dict, List, Optional, Tuple
import uuid

import requests
from dotenv import load_dotenv

from langchain_core.messages import AIMessage, ToolMessage
from langchain_core.messages import HumanMessage, SystemMessage
from langchain_core.runnables import RunnableConfig
from langgraph.graph import StateGraph, START, END
from langgraph.checkpoint.memory import MemorySaver
from langgraph.types import Command

from copilotkit import CopilotKitState
from copilotkit.langgraph import copilotkit_emit_state
from copilotkit.langchain import copilotkit_customize_config

from langchain_google_genai import ChatGoogleGenerativeAI
from pydantic import BaseModel, Field
from langchain_core.tools import tool

load_dotenv()


# Define the agent's runtime state schema for CopilotKit/LangGraph
class StackAgentState(CopilotKitState):
    tool_logs: List[Dict[str, Any]]
    analysis: Dict[str, Any]
    show_cards: bool
    context : Dict[str, Any]
    last_user_content : str


# -------------------- Structured Output Schema --------------------
# Model the structured analysis sections returned by the LLM
class FrontendSpec(BaseModel):
    framework: Optional[str] = None
    language: Optional[str] = None
    package_manager: Optional[str] = None
    styling: Optional[str] = None
    key_libraries: List[str] = Field(default_factory=list)


class BackendSpec(BaseModel):
    framework: Optional[str] = None
    language: Optional[str] = None
    dependency_manager: Optional[str] = None
    key_libraries: List[str] = Field(default_factory=list)
    architecture: Optional[str] = None


class DatabaseSpec(BaseModel):
    type: Optional[str] = None
    notes: Optional[str] = None


class InfrastructureSpec(BaseModel):
    hosting_frontend: Optional[str] = None
    hosting_backend: Optional[str] = None
    dependencies: List[str] = Field(default_factory=list)


class CICDSpec(BaseModel):
    setup: Optional[str] = None


class KeyRootFileSpec(BaseModel):
    file: Optional[str] = None
    description: Optional[str] = None


class HowToRunSpec(BaseModel):
    summary: Optional[str] = None
    steps: List[str] = Field(default_factory=list)


class RiskNoteSpec(BaseModel):
    area: Optional[str] = None
    note: Optional[str] = None


class StructuredStackAnalysis(BaseModel):
    purpose: Optional[str] = None
    frontend: Optional[FrontendSpec] = None
    backend: Optional[BackendSpec] = None
    database: Optional[DatabaseSpec] = None
    infrastructure: Optional[InfrastructureSpec] = None
    ci_cd: Optional[CICDSpec] = None
    key_root_files: List[KeyRootFileSpec] = Field(default_factory=list)
    how_to_run: Optional[HowToRunSpec] = None
    risks_notes: List[RiskNoteSpec] = Field(default_factory=list)



# Expose a tool to return the structured stack analysis to the caller
@tool("return_stack_analysis", args_schema=StructuredStackAnalysis)
def return_stack_analysis_tool(**kwargs) -> Dict[str, Any]:
    """Return the final stack analysis in a strict JSON structure. Use this tool to output results."""
    try:
        validated = StructuredStackAnalysis(**kwargs)
        return validated.model_dump(exclude_none=True)
    except Exception:
        return kwargs


# Parse a GitHub URL and return (owner, repo) when present
def _parse_github_url(url: str) -> Optional[Tuple[str, str]]:
    """Extract owner and repo from a GitHub URL, even if surrounded by other text."""
    pattern = (
        r"https?://github\.com/(?P<owner>[A-Za-z0-9_.-]+)/(?P<repo>[A-Za-z0-9_.-]+)"
    )
    match = re.search(pattern, url)
    if not match:
        return None
    return match.group("owner"), match.group("repo")


# Build GitHub API headers and attach token when available
def _github_headers() -> Dict[str, str]:
    token = os.getenv("GITHUB_TOKEN")
    headers = {"Accept": "application/vnd.github+json"}
    if token:
        headers["Authorization"] = f"Bearer {token}"
    return headers


# Issue a GET request to the GitHub API and return a successful response or None
def _gh_get(url: str) -> Optional[requests.Response]:
    try:
        resp = requests.get(url, headers=_github_headers(), timeout=30)
        if resp.status_code == 200:
            return resp
        return None
    except requests.RequestException:
        return None


# Fetch general repository metadata
def _fetch_repo_info(owner: str, repo: str) -> Dict[str, Any]:
    info = {}
    r = _gh_get(f"https://api.github.com/repos/{owner}/{repo}")
    if r:
        info = r.json()
    return info


# Fetch language usage in bytes for the repository
def _fetch_languages(owner: str, repo: str) -> Dict[str, int]:
    r = _gh_get(f"https://api.github.com/repos/{owner}/{repo}/languages")
    return r.json() if r else {}


# Fetch README content, falling back to scanning root contents when needed
def _fetch_readme(owner: str, repo: str) -> str:
    r = _gh_get(f"https://api.github.com/repos/{owner}/{repo}/readme")
    if r:
        data = r.json()
        content = data.get("content")
        if content:
            try:
                return base64.b64decode(content).decode("utf-8", errors="ignore")
            except Exception:
                pass
    contents = _gh_get(f"https://api.github.com/repos/{owner}/{repo}/contents/")
    if contents:
        for item in contents.json():
            name = item.get("name", "").lower()
            if name in {"readme.md", "readme", "readme.txt", "readme.rst"}:
                file_resp = _gh_get(item.get("download_url", ""))
                if file_resp:
                    return file_resp.text
    return ""


# List files and directories in the repository root
def _list_root(owner: str, repo: str) -> List[Dict[str, Any]]:
    r = _gh_get(f"https://api.github.com/repos/{owner}/{repo}/contents/")
    return r.json() if r else []


# Enumerate common root-level manifest and config files
ROOT_MANIFEST_CANDIDATES = [
    "package.json",
    "pnpm-lock.yaml",
    "yarn.lock",
    "bun.lockb",
    "requirements.txt",
    "pyproject.toml",
    "Pipfile",
    "Pipfile.lock",
    "setup.py",
    "go.mod",
    "pom.xml",
    "build.gradle",
    "build.gradle.kts",
    "Cargo.toml",
    "Gemfile",
    "composer.json",
    "Dockerfile",
    "docker-compose.yml",
    "Procfile",
    "serverless.yml",
    "vercel.json",
    "netlify.toml",
    "next.config.js",
    "next.config.mjs",
    "nuxt.config.js",
    "nuxt.config.ts",
    "angular.json",
    "vite.config.ts",
    "vite.config.js",
]


# Download contents of known manifest files when present in root
def _fetch_manifest_contents(
    owner: str,
    repo: str,
    default_branch: Optional[str],
    root_items: List[Dict[str, Any]],
) -> Dict[str, str]:
    manifest_map: Dict[str, str] = {}
    by_name = {item.get("name"): item for item in root_items}

    for name in ROOT_MANIFEST_CANDIDATES:
        item = by_name.get(name)
        if not item:
            continue
        download_url = item.get("download_url")
        text: Optional[str] = None
        if download_url:
            r = _gh_get(download_url)
            if r:
                text = r.text
        elif default_branch:
            raw_url = f"https://raw.githubusercontent.com/{owner}/{repo}/{default_branch}/{name}"
            r = _gh_get(raw_url)
            if r:
                text = r.text
        if text is not None:
            manifest_map[name] = text
    return manifest_map


# Summarize root items as "name (type)" strings
def _summarize_root_files(root_items: List[Dict[str, Any]]) -> List[str]:
    names = []
    for item in root_items:
        names.append(f"{item.get('name')} ({item.get('type')})")
    return names


# Build the analysis prompt by embedding gathered repository context
def _build_analysis_prompt(context: Dict[str, Any]) -> str:
    return (
        "You are a senior software architect. Analyze the following GitHub repository at a high level.\n"
        "Goals: Provide a concise, structured overview of what the project does and the tech stack.\n\n"
        "Return JSON with keys: purpose, frontend, backend, database, infrastructure, ci_cd, key_root_files, how_to_run, risks_notes.\n\n"
        f"Repository metadata:\n{json.dumps(context.get('repo_info', {}), indent=2)}\n\n"
        f"Languages (bytes of code):\n{json.dumps(context.get('languages', {}), indent=2)}\n\n"
        f"Root items:\n{json.dumps(context.get('root_files', []), indent=2)}\n\n"
        f"Manifests (truncated to first 2000 chars each):\n{json.dumps({k: v[:2000] for k, v in context.get('manifests', {}).items()}, indent=2)}\n\n"
        "README content (truncated to first 8000 chars):\n"
        + context.get("readme", "")[:8000]
        + "\n\n"
        "Infer the stack with specific frameworks and libraries when possible (e.g., Next.js, Express, FastAPI, Prisma, Postgres)."
    )


async def gather_context_node(state: StackAgentState, config: RunnableConfig):
    # 1. Configure execution to emit intermediate messages and tool calls
    config = copilotkit_customize_config(
        config or RunnableConfig(recursion_limit=25),
        emit_messages=True,
        emit_tool_calls=True,
    )

    # Parse the last user message for a GitHub URL; fall back when absent
    last_user_content = state["messages"][-1].content if state["messages"] else ""
    parsed = _parse_github_url(last_user_content)
    
    if not parsed:
        return Command(
            goto= "analyze",
            update = {
                "analysis": state["analysis"],
                "context": {},
                "tool_logs": state["tool_logs"],
                "show_cards": False,
                "last_user_content": last_user_content
            }
        )        
 

    # 2. Create a log entry for URL extraction
    state["tool_logs"] = state.get("tool_logs", [])
    state["tool_logs"].append(
        {
            "id": str(uuid.uuid4()),
            "message": "Getting GitHub URL",
            "status": "processing",
        }
    )
    await copilotkit_emit_state(config, state)


    owner, repo = parsed
    state["tool_logs"][-1]["status"] = "completed"
    await copilotkit_emit_state(config, state)

    # 3. Create a log entry for repository metadata fetch
    state["tool_logs"].append(
        {
            "id": str(uuid.uuid4()),
            "message": "Fetching repository metadata",
            "status": "processing",
        }
    )
    await copilotkit_emit_state(config, state)

    # 4. Fetch metadata, languages, README, root items, and manifests
    repo_info = _fetch_repo_info(owner, repo)
    default_branch = repo_info.get("default_branch")
    languages = _fetch_languages(owner, repo)
    readme = _fetch_readme(owner, repo)
    root_items = _list_root(owner, repo)
    manifests = _fetch_manifest_contents(owner, repo, default_branch, root_items)

    # 5. Assemble the gathered context for downstream analysis
    context: Dict[str, Any] = {
        "owner": owner,
        "repo": repo,
        "repo_info": repo_info,
        "languages": languages,
        "readme": readme,
        "root_files": _summarize_root_files(root_items),
        "manifests": manifests,
    }

    state["tool_logs"][-1]["status"] = "completed"
    await copilotkit_emit_state(config, state)

    return Command(
        goto= "analyze",
        update = {
            "analysis": state["analysis"],
            "context": context,
            "tool_logs": state["tool_logs"],
            "show_cards": False,
            "last_user_content": last_user_content
        }
    )


async def analyze_with_gemini_node(state: StackAgentState, config: RunnableConfig):
    # 6. Short-circuit when no context exists and request a valid URL
    
    context = state.get("context", {})
    if not context:
        state["messages"].append(AIMessage(content= "Please provide a valid GitHub URL"))
        return Command(
            goto= "end",
            update = {
                "messages": state["messages"],
                "show_cards": state["show_cards"],
                "analysis": state["analysis"]
            }
        )

    # 7. Begin analysis and emit progress
    state["tool_logs"] = state.get("tool_logs", [])
    state["tool_logs"].append(
        {"id": str(uuid.uuid4()), "message": "Analyzing stack", "status": "processing"}
    )
    await copilotkit_emit_state(config, state)

    # 8. Build the prompt and system instructions for structured tool usage
    prompt = _build_analysis_prompt(context)
    system_instructions = (
        "You are a senior software architect. Analyze the repository context provided by the user. "
        "When responding, do not write free-form text. Always call the tool `return_stack_analysis` "
        "with all applicable fields filled."
    )
    messages = [
        SystemMessage(content=system_instructions),
        HumanMessage(content=prompt),
    ]

    # 9. Initialize Gemini client for tool call and fallback passes
    model = ChatGoogleGenerativeAI(
        model="gemini-2.5-pro",
        temperature=0.4,
        max_retries=2,
        google_api_key=os.getenv("GOOGLE_API_KEY"),
    )

    pretty: str
    structured_payload: Optional[Dict[str, Any]] = None

    # 10. Attempt tool-based structured output first
    tool_calls = None
    tool_msg = None
    try:
        bound = model.bind_tools([return_stack_analysis_tool])
        tool_msg = await bound.ainvoke(messages, config)
        if isinstance(tool_msg, AIMessage):
            tool_calls = getattr(tool_msg, "tool_calls", None)
            if tool_calls:
                for call in tool_calls:
                    if call.get("name") == "return_stack_analysis":
                        args = call.get("args", {}) or {}
                        state['analysis'] = json.dumps(args)
                        state['show_cards'] = True
                        await copilotkit_emit_state(config, state)
                        try:
                            structured_payload = StructuredStackAnalysis(
                                **args
                            ).model_dump(exclude_none=True)
                        except Exception:
                            structured_payload = dict(args)
                        break
    except Exception:
        pass

    if structured_payload is None:
        # 11. Fall back to schema-coerced structured output if no tool call is returned
        try:
            structured_model = model.with_structured_output(StructuredStackAnalysis)
            structured_response = await structured_model.ainvoke(messages, config)
            if isinstance(structured_response, StructuredStackAnalysis):
                structured_payload = structured_response.model_dump(exclude_none=True)
            elif isinstance(structured_response, dict):
                structured_payload = structured_response
            else:
                try:
                    structured_payload = structured_response.dict(exclude_none=True)  # type: ignore[attr-defined]
                except Exception:
                    structured_payload = None
        except Exception:
            structured_payload = None

    # 12. Mark the analysis step complete and prepare a concise summary request
    state["tool_logs"][-1]["status"] = "completed"
    await copilotkit_emit_state(config, state)
    messages[-1].content = state["last_user_content"]
    if tool_calls and tool_msg:
        messages.append(AIMessage(tool_calls=tool_calls, id=tool_msg.id, type="ai", content=''))
        messages.append(ToolMessage(content="The GitHub Repository has been analyzed", tool_call_id=tool_calls[0]["id"], type="tool"))
    messages[0].content = "Generate a summary of the GitHub Repository. It should be in a concise and strictly textual"
    
    # 13. Generate a user-facing summary referencing the tool call outcome
    client = ChatGoogleGenerativeAI(
        model="gemini-2.5-pro",
        temperature=0.4,
        max_retries=2,
        google_api_key=os.getenv("GOOGLE_API_KEY"),
    )
    state["tool_logs"].append({"id": str(uuid.uuid4()), "message": "Generating Summary", "status": "processing"})
    await copilotkit_emit_state(config, state)
    model_response = await client.ainvoke(messages, config)
    state["tool_logs"][-1]["status"] = "completed"
    await copilotkit_emit_state(config, state)
    state["messages"].append(AIMessage(content=model_response.content))
    # 14. Return a message containing the analysis
    return Command(
        goto= "end",
        update = {
            "messages": state["messages"],
            "show_cards": True,
            "analysis": state["analysis"]
        }
    )


async def end_node(state: StackAgentState, config: RunnableConfig):
    # 15. Finalize the workflow and emit one last state update
    # Clear logs and emit once more to update UI
    state["tool_logs"] = []
    await copilotkit_emit_state(config or RunnableConfig(recursion_limit=25), state)
    return Command(
        goto= END,
        update = {
            "messages": state["messages"],
            "show_cards": state["show_cards"],
            "analysis": state["analysis"]
        }
    )


workflow = StateGraph(StackAgentState)
workflow.add_node("gather_context", gather_context_node)
workflow.add_node("analyze", analyze_with_gemini_node)
workflow.add_node("end", end_node)
workflow.add_edge(START, "gather_context")
workflow.add_edge("gather_context", "analyze")
workflow.add_edge("analyze", END)
workflow.set_entry_point("gather_context")
workflow.set_finish_point("end")

stack_analysis_graph = workflow.compile(checkpointer=MemorySaver())
