from fastapi import APIRouter, Depends, HTTPException, Request
from sqlalchemy.orm import Session
from sqlalchemy import and_, or_
from pydantic import BaseModel
from typing import Optional, List
import json

from database import get_db
from models import User, Conversation, ConversationMember, Message, Group, GroupMember, GroupMessage
from auth import get_current_user_from_header, user_to_dict

router = APIRouter()

# ─── Users ───────────────────────────────────────────────────────────────────

@router.get("/users/search")
def search_users(q: str, request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)
    users = db.query(User).filter(
        User.id != me.id,
        User.username.ilike(f"%{q}%") if q else True
    ).limit(20).all()
    return [user_to_dict(u) for u in users]

@router.get("/users/{user_id}/public_key")
def get_public_key(user_id: int, request: Request, db: Session = Depends(get_db)):
    get_current_user_from_header(request, db)
    user = db.query(User).filter(User.id == user_id).first()
    if not user:
        raise HTTPException(status_code=404, detail="User not found")
    return {"public_key": user.public_key}

# ─── DM Conversations ─────────────────────────────────────────────────────────

@router.post("/conversations")
def get_or_create_conversation(target_user_id: int, request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)

    # Find existing conversation between the two users
    my_convs = db.query(ConversationMember.conversation_id).filter(ConversationMember.user_id == me.id)
    their_convs = db.query(ConversationMember.conversation_id).filter(ConversationMember.user_id == target_user_id)
    common = my_convs.intersect(their_convs).all()

    if common:
        conv_id = common[0][0]
        conv = db.query(Conversation).filter(Conversation.id == conv_id).first()
    else:
        conv = Conversation()
        db.add(conv)
        db.flush()
        db.add(ConversationMember(conversation_id=conv.id, user_id=me.id))
        db.add(ConversationMember(conversation_id=conv.id, user_id=target_user_id))
        db.commit()
        db.refresh(conv)

    other = db.query(User).filter(User.id == target_user_id).first()
    return {
        "id": conv.id,
        "other_user": user_to_dict(other),
        "messages": [msg_to_dict(m, me.id) for m in conv.messages[-50:]]
    }

@router.get("/conversations")
def list_conversations(request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)
    memberships = db.query(ConversationMember).filter(ConversationMember.user_id == me.id).all()
    result = []
    for m in memberships:
        conv = m.conversation
        other_member = next((x for x in conv.members if x.user_id != me.id), None)
        if not other_member:
            continue
        other = other_member.user
        last_msg = conv.messages[-1] if conv.messages else None
        result.append({
            "id": conv.id,
            "other_user": user_to_dict(other),
            "last_message_at": last_msg.created_at.isoformat() if last_msg and hasattr(last_msg.created_at, 'isoformat') else str(last_msg.created_at) if last_msg else None,
            "unread_count": sum(1 for msg in conv.messages if not msg.is_read and msg.sender_id != me.id)
        })
    result.sort(key=lambda x: x["last_message_at"] or "", reverse=True)
    return result

@router.delete("/conversations/{conversation_id}")
def delete_conversation(conversation_id: int, request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)
    membership = db.query(ConversationMember).filter(
        ConversationMember.conversation_id == conversation_id,
        ConversationMember.user_id == me.id
    ).first()
    if not membership:
        raise HTTPException(status_code=404, detail="Conversation not found")
    db.delete(membership)
    db.commit()
    return {"ok": True}

# ─── Groups ───────────────────────────────────────────────────────────────────

class CreateGroupRequest(BaseModel):
    name: str
    description: Optional[str] = None
    member_ids: List[int] = []

class AddMemberRequest(BaseModel):
    user_id: int

@router.post("/groups")
def create_group(req: CreateGroupRequest, request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)
    group = Group(name=req.name, description=req.description, created_by=me.id)
    db.add(group)
    db.flush()

    # Add creator as admin
    db.add(GroupMember(group_id=group.id, user_id=me.id, role="admin"))

    # Add other members
    for uid in req.member_ids:
        if uid != me.id:
            db.add(GroupMember(group_id=group.id, user_id=uid))

    db.commit()
    db.refresh(group)
    return group_to_dict(group, me.id)

@router.get("/groups")
def list_groups(request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)
    memberships = db.query(GroupMember).filter(GroupMember.user_id == me.id).all()
    return [group_to_dict(m.group, me.id) for m in memberships]

@router.get("/groups/{group_id}")
def get_group(group_id: int, request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)
    group = db.query(Group).filter(Group.id == group_id).first()
    if not group:
        raise HTTPException(status_code=404, detail="Group not found")
    membership = db.query(GroupMember).filter(
        GroupMember.group_id == group_id,
        GroupMember.user_id == me.id
    ).first()
    if not membership:
        raise HTTPException(status_code=403, detail="Not a member")
    return {
        **group_to_dict(group, me.id),
        "messages": [group_msg_to_dict(m, me.id) for m in group.messages[-50:]],
        "members": [{"user": user_to_dict(m.user), "role": m.role} for m in group.members]
    }

@router.post("/groups/{group_id}/members")
def add_member(group_id: int, req: AddMemberRequest, request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)
    membership = db.query(GroupMember).filter(
        GroupMember.group_id == group_id,
        GroupMember.user_id == me.id
    ).first()
    if not membership:
        raise HTTPException(status_code=403, detail="Not a member")

    existing = db.query(GroupMember).filter(
        GroupMember.group_id == group_id,
        GroupMember.user_id == req.user_id
    ).first()
    if existing:
        raise HTTPException(status_code=400, detail="Already a member")

    db.add(GroupMember(group_id=group_id, user_id=req.user_id))
    db.commit()
    user = db.query(User).filter(User.id == req.user_id).first()
    return {"ok": True, "user": user_to_dict(user)}

@router.delete("/groups/{group_id}/members/{user_id}")
def remove_member(group_id: int, user_id: int, request: Request, db: Session = Depends(get_db)):
    me = get_current_user_from_header(request, db)
    membership = db.query(GroupMember).filter(
        GroupMember.group_id == group_id,
        GroupMember.user_id == me.id
    ).first()
    if not membership:
        raise HTTPException(status_code=403, detail="Not a member")
    m = db.query(GroupMember).filter(GroupMember.group_id == group_id, GroupMember.user_id == user_id).first()
    if m:
        db.delete(m)
        db.commit()
    return {"ok": True}

# ─── Helpers ──────────────────────────────────────────────────────────────────

def msg_to_dict(msg: Message, viewer_id: int) -> dict:
    is_sender = msg.sender_id == viewer_id
    return {
        "id": msg.id,
        "sender_id": msg.sender_id,
        "sender_name": msg.sender.display_name if msg.sender else "Unknown",
        "ciphertext": msg.ciphertext_for_sender if is_sender else msg.ciphertext_for_recipient,
        "created_at": msg.created_at.isoformat() if hasattr(msg.created_at, 'isoformat') else str(msg.created_at),
        "is_read": msg.is_read,
    }

def group_msg_to_dict(msg: GroupMessage, viewer_id: int) -> dict:
    keys = json.loads(msg.encrypted_aes_keys) if msg.encrypted_aes_keys else {}
    return {
        "id": msg.id,
        "sender_id": msg.sender_id,
        "sender_name": msg.sender.display_name if msg.sender else "Unknown",
        "ciphertext": msg.ciphertext,
        "iv": msg.iv,
        "encrypted_aes_key": keys.get(str(viewer_id)),
        "created_at": msg.created_at.isoformat() if hasattr(msg.created_at, 'isoformat') else str(msg.created_at),
    }

def group_to_dict(group: Group, viewer_id: int) -> dict:
    return {
        "id": group.id,
        "name": group.name,
        "description": group.description,
        "created_by": group.created_by,
        "avatar_color": group.avatar_color,
        "member_count": len(group.members),
        "created_at": group.created_at.isoformat() if hasattr(group.created_at, 'isoformat') else str(group.created_at),
    }