"""Projects (Native PM Construction Platform Projects).

Supports:
- Project list with real-time statistics and scoping.
- Creation, editing, archiving of native projects.
- Project team members management.
- Unique project code and UUID resolution.
"""
from __future__ import annotations

import uuid
from datetime import date
from typing import Any

from fastapi import APIRouter, Depends, HTTPException
from pydantic import BaseModel, Field
from sqlalchemy import func, or_, select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.authz import AuthContext, Perm, require_permission
from app.db import get_db
from app.errors import NotFoundError, ValidationError
from app.models import (
    Project,
    ProjectMember,
    ProjectStatus,
    Task,
    TaskRelation,
    TaskRelationType,
)
from app.scheduling_service import (
    calculate_schedule,
    check_for_cycle,
    rollup_parent_tasks,
    sync_project_lifecycle_dates,
)
from app.serializers import _iso, project_dict, project_member_dict, task_relation_dict
from app.utils.date_service import date_service
from app.utils.jalali import to_jalali_str

router = APIRouter(prefix="/projects", tags=["projects"])

ACTIVE_QC = ("pre_qc_pending", "exec_qc_pending", "ready")
FAILED_QC = ("pre_qc_failed", "qc_failed_rework")

view_projects = require_permission(Perm.projects_view)
manage_projects = require_permission(Perm.projects_create)


class ProjectCreateSchema(BaseModel):
    name: str = Field(..., min_length=1, max_length=255)
    description: str = ""
    location: str = ""
    project_manager: str = ""
    planned_start: str | None = None
    planned_end: str | None = None
    status: str = ProjectStatus.ACTIVE.value


class ProjectUpdateSchema(BaseModel):
    name: str | None = None
    description: str | None = None
    location: str | None = None
    project_manager: str | None = None
    planned_start: str | None = None
    planned_end: str | None = None
    actual_start: str | None = None
    actual_end: str | None = None
    status: str | None = None
    progress: float | None = None


class ProjectMemberCreateSchema(BaseModel):
    user_id: str
    role: str = "site_engineer"


class ErpMappingSchema(BaseModel):
    erp_project_id: str | None = None


class TaskRelationCreateSchema(BaseModel):
    from_task_id: str
    to_task_id: str
    relation_type: str = "FS"
    lag_days: int = 0


class TaskRelationUpdateSchema(BaseModel):
    """Edit an existing dependency. The endpoints (from/to tasks) are immutable —
    changing them is a different relation, so it must be deleted and recreated."""

    relation_type: str | None = None
    lag_days: int | None = None


async def _resolve_project(db: AsyncSession, ctx: AuthContext, project_id_or_op: str | int) -> Project:
    """Find a project by UUID and enforce scope."""
    query = select(Project).options(
        selectinload(Project.members).selectinload(ProjectMember.user)
    )

    try:
        val_uuid = uuid.UUID(str(project_id_or_op))
        stmt = query.where(Project.id == val_uuid)
    except ValueError:
        raise NotFoundError("شناسه پروژه نامعتبر است")

    project = (await db.execute(stmt)).scalar_one_or_none()
    if not project:
        raise NotFoundError("پروژه مورد نظر یافت نشد")
    ctx.ensure_native_project(project.id)
    return project


async def native_project_stats(db: AsyncSession, project_id: uuid.UUID) -> dict:
    """Task counters of one native project."""
    today = date_service.today()
    rows = (
        await db.execute(
            select(Task.qc_status, Task.planned_end, Task.status, func.count())
            .where(Task.project_id == project_id)
            .group_by(Task.qc_status, Task.planned_end, Task.status)
        )
    ).all()

    total = sum(r[3] for r in rows)
    completed = sum(r[3] for r in rows if r[2] == "COMPLETED")
    in_progress = sum(r[3] for r in rows if r[2] == "IN_PROGRESS")
    blocked = sum(r[3] for r in rows if r[2] == "BLOCKED")
    awaiting = sum(r[3] for r in rows if r[0] in ACTIVE_QC)
    failed = sum(r[3] for r in rows if r[0] in FAILED_QC)
    overdue = sum(r[3] for r in rows if r[2] != "COMPLETED" and r[1] and r[1] < today)

    return {
        "total": total,
        "completed": completed,
        "in_progress": in_progress,
        "blocked": blocked,
        "awaiting_qc": awaiting,
        "failed_qc": failed,
        "overdue": overdue,
    }


@router.get("")
async def list_projects(
    ctx: AuthContext = Depends(view_projects),
    db: AsyncSession = Depends(get_db),
):
    """List all projects visible to the user, with stats and team counts."""
    stmt = select(Project).options(selectinload(Project.members)).order_by(Project.created_at.desc())

    # Apply project scoping for supervisor / scoped roles (native projects = UUID)
    stmt = ctx.scope_native(stmt, Project.id)

    projects = (await db.execute(stmt)).scalars().all()
    results = []
    for p in projects:
        stats = await native_project_stats(db, p.id)
        results.append(project_dict(p, member_count=len(p.members), task_stats=stats))

    return {"data": results}


@router.post("")
async def create_project(
    payload: ProjectCreateSchema,
    ctx: AuthContext = Depends(manage_projects),
    db: AsyncSession = Depends(get_db),
):
    """Create a new native project."""
    p_start = date_service.parse(payload.planned_start) if payload.planned_start else None
    p_end = date_service.parse(payload.planned_end) if payload.planned_end else None
    if p_start and p_end and p_end < p_start:
        raise ValidationError("تاریخ پایان نمی‌تواند قبل از تاریخ شروع باشد", field="planned_end")

    project = Project(
        name=payload.name.strip(),
        description=payload.description.strip(),
        location=payload.location.strip() if payload.location else "",
        project_manager=payload.project_manager.strip() if payload.project_manager else ctx.user.display_name,
        planned_start=p_start,
        planned_end=p_end,
        status=payload.status.upper(),
    )
    db.add(project)
    await db.flush()

    # Automatically add the creator as a project manager member
    creator_member = ProjectMember(
        project_id=project.id,
        user_id=ctx.user.id,
        role="project_manager",
    )
    db.add(creator_member)
    await db.commit()
    await db.refresh(project)

    stats = {"total": 0, "completed": 0, "in_progress": 0, "blocked": 0, "overdue": 0}
    res = project_dict(project, member_count=1, task_stats=stats)
    res["identifier"] = str(project.id)
    return {"data": res}


@router.get("/{id}")
async def get_project(
    id: str,
    ctx: AuthContext = Depends(view_projects),
    db: AsyncSession = Depends(get_db),
):
    """Get project details, member list, and overall stats."""
    project = await _resolve_project(db, ctx, id)
    stats = await native_project_stats(db, project.id)

    data = project_dict(project, member_count=len(project.members), task_stats=stats)
    data["identifier"] = str(project.id)
    data["members"] = [project_member_dict(m) for m in project.members]
    return {"data": data}


@router.patch("/{id}")
async def update_project(
    id: str,
    payload: ProjectUpdateSchema,
    ctx: AuthContext = Depends(require_permission(Perm.projects_update)),
    db: AsyncSession = Depends(get_db),
):
    """Update project details, status, or dates."""
    project = await _resolve_project(db, ctx, id)

    if payload.name is not None:
        project.name = payload.name.strip()
    if payload.description is not None:
        project.description = payload.description.strip()
    if payload.location is not None:
        project.location = payload.location.strip()
    if payload.project_manager is not None:
        project.project_manager = payload.project_manager.strip()
    if payload.status is not None:
        project.status = payload.status.upper()
    if payload.progress is not None:
        project.progress = max(0.0, min(100.0, payload.progress))

    if payload.planned_start is not None:
        project.planned_start = date_service.parse(payload.planned_start)
    if payload.planned_end is not None:
        project.planned_end = date_service.parse(payload.planned_end)
    if payload.actual_start is not None:
        project.actual_start = date_service.parse(payload.actual_start)
    if payload.actual_end is not None:
        project.actual_end = date_service.parse(payload.actual_end)

    if project.planned_start and project.planned_end and project.planned_end < project.planned_start:
        raise ValidationError("تاریخ پایان نمی‌تواند قبل از تاریخ شروع باشد", field="planned_end")

    await db.commit()
    await db.refresh(project)
    stats = await native_project_stats(db, project.id)
    return {"data": project_dict(project, member_count=len(project.members), task_stats=stats)}


@router.post("/{id}/members")
async def add_project_member(
    id: str,
    payload: ProjectMemberCreateSchema,
    ctx: AuthContext = Depends(require_permission(Perm.projects_update)),
    db: AsyncSession = Depends(get_db),
):
    """Add a team member to the project."""
    project = await _resolve_project(db, ctx, id)
    target_user_id = uuid.UUID(payload.user_id)

    # Check if already a member
    existing = await db.scalar(
        select(ProjectMember).where(
            ProjectMember.project_id == project.id, ProjectMember.user_id == target_user_id
        )
    )
    if existing:
        existing.role = payload.role
    else:
        member = ProjectMember(
            project_id=project.id,
            user_id=target_user_id,
            role=payload.role,
        )
        db.add(member)

    await db.commit()
    # Return updated members list
    await db.refresh(project)
    project = await _resolve_project(db, ctx, project.id)
    return {"data": [project_member_dict(m) for m in project.members]}


@router.delete("/{id}/members/{user_id}")
async def remove_project_member(
    id: str,
    user_id: str,
    ctx: AuthContext = Depends(require_permission(Perm.projects_update)),
    db: AsyncSession = Depends(get_db),
):
    """Remove a team member from the project."""
    project = await _resolve_project(db, ctx, id)
    target_user_id = uuid.UUID(user_id)

    member = await db.scalar(
        select(ProjectMember).where(
            ProjectMember.project_id == project.id, ProjectMember.user_id == target_user_id
        )
    )
    if member:
        await db.delete(member)
        await db.commit()

    project = await _resolve_project(db, ctx, project.id)
    return {"data": [project_member_dict(m) for m in project.members]}


@router.patch("/{id}/erp-mapping")
async def map_erp_project(
    id: str,
    payload: ErpMappingSchema,
    ctx: AuthContext = Depends(require_permission(Perm.projects_update)),
    db: AsyncSession = Depends(get_db),
):
    project = await _resolve_project(db, ctx, id)
    return {"data": {"id": str(project.id)}}


# --- Relations & Dependencies ---

@router.get("/{id}/relations")
async def list_project_relations(
    id: str,
    ctx: AuthContext = Depends(view_projects),
    db: AsyncSession = Depends(get_db),
):
    """List all task dependencies in a project."""
    project = await _resolve_project(db, ctx, id)
    stmt = (
        select(TaskRelation)
        .options(selectinload(TaskRelation.from_task), selectinload(TaskRelation.to_task))
        .where(TaskRelation.project_id == project.id)
    )
    relations = (await db.execute(stmt)).scalars().all()
    return {"data": [task_relation_dict(r) for r in relations]}


@router.post("/{id}/relations")
async def create_task_relation(
    id: str,
    payload: TaskRelationCreateSchema,
    ctx: AuthContext = Depends(require_permission(Perm.tasks_create)),
    db: AsyncSession = Depends(get_db),
):
    """Create a new task dependency (FS, SS, FF, SF + lag). Enforces cycle check."""
    project = await _resolve_project(db, ctx, id)
    from_id = uuid.UUID(payload.from_task_id)
    to_id = uuid.UUID(payload.to_task_id)

    if from_id == to_id:
        raise ValidationError("یک وظیفه نمی‌تواند پیش‌نیاز خودش باشد")

    # Verify tasks belong to this project
    from_task = await db.get(Task, from_id)
    to_task = await db.get(Task, to_id)
    if not from_task or from_task.project_id != project.id:
        raise ValidationError("وظیفه پیش‌نیاز در این پروژه یافت نشد")
    if not to_task or to_task.project_id != project.id:
        raise ValidationError("وظیفه وابسته در این پروژه یافت نشد")

    # Load existing relations to verify DAG
    existing_rels = (
        await db.execute(select(TaskRelation.from_task_id, TaskRelation.to_task_id).where(TaskRelation.project_id == project.id))
    ).all()
    existing_pairs = [(r[0], r[1]) for r in existing_rels]

    # Check for duplicate
    if (from_id, to_id) in existing_pairs:
        raise ValidationError("این وابستگی قبلاً ثبت شده است")

    # Cycle check
    if check_for_cycle(existing_pairs, from_id, to_id):
        raise ValidationError("این وابستگی باعث ایجاد چرخه (حلقه تکرار) در ساختار زمان‌بندی می‌شود")

    rtype = payload.relation_type.upper()
    if rtype not in ("FS", "SS", "FF", "SF"):
        raise ValidationError("نوع وابستگی باید یکی از مقادیر FS، SS، FF، SF باشد")

    relation = TaskRelation(
        project_id=project.id,
        from_task_id=from_id,
        to_task_id=to_id,
        relation_type=rtype,
        lag_days=payload.lag_days,
    )
    db.add(relation)
    await db.commit()

    # Recalculate schedule cascade automatically
    all_tasks = (await db.execute(select(Task).where(Task.project_id == project.id))).scalars().all()
    all_relations = (await db.execute(select(TaskRelation).where(TaskRelation.project_id == project.id))).scalars().all()
    sched_result = calculate_schedule(all_tasks, all_relations, project.planned_start)

    # Update tasks with new early dates if changed
    for t in all_tasks:
        if t.id in sched_result["tasks_schedule"]:
            info = sched_result["tasks_schedule"][t.id]
            t.planned_start = info["planned_start"]
            t.planned_end = info["planned_end"]
            t.duration = info["duration"]
    await db.commit()

    await db.refresh(relation)
    return {"data": task_relation_dict(relation, from_task.title, to_task.title)}


@router.patch("/{id}/relations/{relation_id}")
async def update_task_relation(
    id: str,
    relation_id: str,
    payload: TaskRelationUpdateSchema,
    ctx: AuthContext = Depends(require_permission(Perm.tasks_create)),
    db: AsyncSession = Depends(get_db),
):
    """Edit a dependency's type and/or lag, then re-run the schedule cascade."""
    project = await _resolve_project(db, ctx, id)
    rel = await db.scalar(
        select(TaskRelation)
        .options(selectinload(TaskRelation.from_task), selectinload(TaskRelation.to_task))
        .where(TaskRelation.id == uuid.UUID(relation_id), TaskRelation.project_id == project.id)
    )
    if rel is None:
        raise NotFoundError("وابستگی یافت نشد")

    if payload.relation_type is not None:
        rtype = payload.relation_type.upper()
        if rtype not in ("FS", "SS", "FF", "SF"):
            raise ValidationError("نوع وابستگی باید یکی از مقادیر FS، SS، FF، SF باشد")
        rel.relation_type = rtype
    if payload.lag_days is not None:
        rel.lag_days = payload.lag_days
    await db.commit()

    # Recalculate the schedule so the edit takes effect immediately
    all_tasks = (await db.execute(select(Task).where(Task.project_id == project.id))).scalars().all()
    all_relations = (await db.execute(select(TaskRelation).where(TaskRelation.project_id == project.id))).scalars().all()
    sched_result = calculate_schedule(all_tasks, all_relations, project.planned_start)
    for t in all_tasks:
        if t.id in sched_result["tasks_schedule"]:
            info = sched_result["tasks_schedule"][t.id]
            t.planned_start = info["planned_start"]
            t.planned_end = info["planned_end"]
            t.duration = info["duration"]
    await db.commit()

    await db.refresh(rel)
    return {"data": task_relation_dict(rel, rel.from_task.title, rel.to_task.title)}


@router.delete("/{id}/relations/{relation_id}")
async def delete_task_relation(
    id: str,
    relation_id: str,
    ctx: AuthContext = Depends(require_permission(Perm.tasks_delete)),
    db: AsyncSession = Depends(get_db),
):
    """Delete a task dependency."""
    project = await _resolve_project(db, ctx, id)
    rel_uuid = uuid.UUID(relation_id)
    rel = await db.scalar(
        select(TaskRelation).where(TaskRelation.id == rel_uuid, TaskRelation.project_id == project.id)
    )
    if rel:
        await db.delete(rel)
        await db.commit()
    return {"data": {"deleted": True}}


# --- Interactive Gantt & Topological Scheduling ---

@router.get("/{id}/gantt")
async def get_project_gantt(
    id: str,
    ctx: AuthContext = Depends(view_projects),
    db: AsyncSession = Depends(get_db),
):
    """Return full Gantt chart dataset with CPM calculations, relations, and critical path."""
    project = await _resolve_project(db, ctx, id)

    # 1. Fetch tasks, relations, milestones
    tasks = (
        await db.execute(
            select(Task)
            .options(selectinload(Task.children))
            .where(Task.project_id == project.id)
            .order_by(Task.planned_start.asc().nulls_last(), Task.created_at.asc())
        )
    ).scalars().all()

    relations = (
        await db.execute(
            select(TaskRelation)
            .options(selectinload(TaskRelation.from_task), selectinload(TaskRelation.to_task))
            .where(TaskRelation.project_id == project.id)
        )
    ).scalars().all()

    # 2. Run CPM scheduling analysis
    sched = calculate_schedule(tasks, relations, project.planned_start)
    sched_info = sched["tasks_schedule"]
    crit_set = set(sched["critical_path"])

    # 3. Format tasks
    formatted_tasks = []
    for t in tasks:
        t_sched = sched_info.get(t.id, {})
        start_dt = t_sched.get("planned_start") or t.planned_start
        end_dt = t_sched.get("planned_end") or t.planned_end
        formatted_tasks.append({
            "id": str(t.id),
            "title": t.title,
            "subject": t.title,
            "parent_id": str(t.parent_id) if t.parent_id else None,
            "status": t.status,
            "priority": t.priority,
            "planned_start": _iso(start_dt),
            "planned_end": _iso(end_dt),
            "planned_start_jalali": to_jalali_str(start_dt),
            "planned_end_jalali": to_jalali_str(end_dt),
            "duration": t_sched.get("duration") or t.duration or 1,
            "progress": t.progress or 0,
            "is_critical": t.id in crit_set,
            "float_days": t_sched.get("float_days", 0),
            "qc_status": t.qc_status or "none",
            "assignee_name": t.assignee_name or (t.assignee.display_name if getattr(t, "assignee", None) else None),
        })

    return {
        "data": {
            "project": {
                "id": str(project.id),
                "identifier": str(project.id),
                "name": project.name,
                "planned_start": _iso(project.planned_start),
                "planned_end": _iso(project.planned_end),
                "planned_start_jalali": to_jalali_str(project.planned_start),
                "planned_end_jalali": to_jalali_str(project.planned_end),
                "progress": project.progress,
            },
            "tasks": formatted_tasks,
            "relations": [task_relation_dict(r) for r in relations],
            "critical_path": [str(tid) for tid in sched["critical_path"]],
            "project_finish": _iso(sched.get("project_finish")),
            "project_finish_jalali": to_jalali_str(sched.get("project_finish")),
        }
    }


@router.post("/{id}/reschedule")
async def reschedule_project(
    id: str,
    ctx: AuthContext = Depends(require_permission(Perm.projects_update)),
    db: AsyncSession = Depends(get_db),
):
    """Trigger full topological forward-pass recalculation and persist cascaded dates."""
    project = await _resolve_project(db, ctx, id)

    tasks = (await db.execute(select(Task).where(Task.project_id == project.id))).scalars().all()
    relations = (await db.execute(select(TaskRelation).where(TaskRelation.project_id == project.id))).scalars().all()

    sched = calculate_schedule(tasks, relations, project.planned_start)
    sched_info = sched["tasks_schedule"]

    updated_count = 0
    for t in tasks:
        if t.id in sched_info:
            info = sched_info[t.id]
            t.planned_start = info["planned_start"]
            t.planned_end = info["planned_end"]
            t.duration = info["duration"]
            updated_count += 1

    # Roll up summary tasks
    rollups = rollup_parent_tasks(tasks)
    for pid, rdata in rollups.items():
        parent_task = await db.get(Task, pid)
        if parent_task:
            if rdata["planned_start"]:
                parent_task.planned_start = rdata["planned_start"]
            if rdata["planned_end"]:
                parent_task.planned_end = rdata["planned_end"]
            if rdata.get("duration"):
                parent_task.duration = rdata["duration"]

    await sync_project_lifecycle_dates(db, project.id)
    await db.commit()
    return {"data": {"recalculated": True, "tasks_updated": updated_count}}