"""Shared project commit logic.

Used by the COMMIT_PROJECT websocket handler ("Commit"), which durably commits
to Project History as part of the student action.

Snapshots are written under ~/.studybuddy/sessions/ -> that is where the history
listing and resume endpoints (app.routers.library) read from. The primary,
history-facing file is doc_{document_id}.json (one per document set, so re-uploading
the same papers resumes the same project); {project_id}.json and latest.json are
written alongside for convenience. (~/.studybuddy/projects/ is the upload root, a
separate concern -> do not write snapshots there or history won't find them.)
"""
import json
import os
from typing import Any, Dict, List

_SESSIONS_DIR = os.path.expanduser("~/.studybuddy/sessions")

_brain = None


def _get_brain():
    global _brain
    if _brain is None:
        from app.agents.brain_agent import BrainAgent
        _brain = BrainAgent()
    return _brain


async def commit_project_snapshot(
    project_id: str,
    topic: str,
    intention: str,
    nodes: List[Dict[str, Any]],
    content_files: List[str] = None,
    document_id: str = "",
    file_ids: List[str] = None,
) -> Dict[str, Any]:
    content_files = content_files or []
    file_ids = file_ids or []

    os.makedirs(_SESSIONS_DIR, exist_ok=True)

    # A title should describe the project once, not change on every Commit -> reuse
    # whatever was already generated for this document set if it exists. Keyed by
    # document_id (the history/dedup key) so the title is stable across resumes.
    title = ""
    doc_path = os.path.join(_SESSIONS_DIR, f"doc_{document_id}.json") if document_id else ""
    if doc_path and os.path.exists(doc_path):
        try:
            with open(doc_path, encoding="utf-8") as f:
                title = json.load(f).get("title", "")
        except Exception:
            pass
    if not title:
        try:
            title = _get_brain().generate_session_title(topic, content_files, intention)
        except Exception:
            title = topic or "Study Project"

    payload = {
        "project_id": project_id,
        "topic": topic,
        "intention": intention,
        "nodes": nodes,
        "content_files": content_files,
        "document_id": document_id,  # internal cache key + history/dedup key
        "file_ids": file_ids,
        "title": title,
    }

    # doc_{document_id}.json is the file the history listing/resume endpoints read
    # (keyed by document set); {project_id}.json + latest.json are written alongside.
    paths = [os.path.join(_SESSIONS_DIR, f"{project_id}.json"),
             os.path.join(_SESSIONS_DIR, "latest.json")]
    if document_id:
        paths.append(os.path.join(_SESSIONS_DIR, f"doc_{document_id}.json"))
    for path in paths:
        with open(path, "w", encoding="utf-8") as f:
            json.dump(payload, f, indent=2)

    # Record the temporal Commit event without copying snapshot JSON into
    # semantic memory; Project History already owns the complete snapshot.
    from app.services.student_memory import StudentMemoryService
    await StudentMemoryService().stage_project_snapshot(project_id, "")

    return {"status": "committed", "paths": paths}