from fastapi import APIRouter, Depends
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, func
from ..database import get_db
from ..models import TokenUsage, Student

router = APIRouter(prefix="/api/analytics", tags=["Analytics"])

# GPT-4o-mini pricing (per 1M tokens)
INPUT_COST_PER_M = 0.15
OUTPUT_COST_PER_M = 0.60

EVENT_LABELS = {
    "syllabus_analysis": "Syllabus Analysis",
    "test_generation": "Test Paper Generation",
    "answer_evaluation": "Answer Evaluation",
    "performance_analysis": "Performance Analysis",
    "targeted_test_generation": "Targeted Test Generation",
}


def calc_cost(input_tokens: int, output_tokens: int) -> float:
    return round(
        (input_tokens / 1_000_000) * INPUT_COST_PER_M
        + (output_tokens / 1_000_000) * OUTPUT_COST_PER_M,
        6,
    )


@router.get("/overview")
async def get_overview(db: AsyncSession = Depends(get_db)):
    result = await db.execute(select(TokenUsage).order_by(TokenUsage.created_at.desc()))
    rows = result.scalars().all()

    total_input = sum(r.input_tokens for r in rows)
    total_output = sum(r.output_tokens for r in rows)
    total_tokens = sum(r.total_tokens for r in rows)

    by_event: dict[str, dict] = {}
    for r in rows:
        et = r.event_type
        if et not in by_event:
            by_event[et] = {"event_type": et, "label": EVENT_LABELS.get(et, et),
                            "count": 0, "input_tokens": 0, "output_tokens": 0, "total_tokens": 0}
        by_event[et]["count"] += 1
        by_event[et]["input_tokens"] += r.input_tokens
        by_event[et]["output_tokens"] += r.output_tokens
        by_event[et]["total_tokens"] += r.total_tokens

    for et in by_event:
        by_event[et]["cost_usd"] = calc_cost(by_event[et]["input_tokens"], by_event[et]["output_tokens"])

    return {
        "total_events": len(rows),
        "total_input_tokens": total_input,
        "total_output_tokens": total_output,
        "total_tokens": total_tokens,
        "estimated_cost_usd": calc_cost(total_input, total_output),
        "by_event_type": sorted(by_event.values(), key=lambda x: x["total_tokens"], reverse=True),
        "model": rows[0].model if rows else "—",
    }


@router.get("/by-student")
async def get_by_student(db: AsyncSession = Depends(get_db)):
    result = await db.execute(select(TokenUsage).where(TokenUsage.student_id.isnot(None)))
    rows = result.scalars().all()

    students_result = await db.execute(select(Student).order_by(Student.created_at.asc()))
    students = students_result.scalars().all()
    student_code_map = {s.id: f"STU-{i+1:03d}" for i, s in enumerate(students)}

    by_student: dict[str, dict] = {}
    for r in rows:
        sid = r.student_id
        if sid not in by_student:
            by_student[sid] = {
                "student_id": sid,
                "student_name": r.student_name or "Unknown",
                "student_code": student_code_map.get(sid, "—"),
                "total_tokens": 0,
                "input_tokens": 0,
                "output_tokens": 0,
                "event_count": 0,
                "by_event": {},
            }
        by_student[sid]["total_tokens"] += r.total_tokens
        by_student[sid]["input_tokens"] += r.input_tokens
        by_student[sid]["output_tokens"] += r.output_tokens
        by_student[sid]["event_count"] += 1
        et = r.event_type
        by_student[sid]["by_event"][et] = by_student[sid]["by_event"].get(et, 0) + r.total_tokens

    for sid in by_student:
        by_student[sid]["cost_usd"] = calc_cost(
            by_student[sid]["input_tokens"], by_student[sid]["output_tokens"]
        )

    return sorted(by_student.values(), key=lambda x: x["total_tokens"], reverse=True)


@router.get("/events")
async def get_events(limit: int = 100, db: AsyncSession = Depends(get_db)):
    result = await db.execute(
        select(TokenUsage).order_by(TokenUsage.created_at.desc()).limit(limit)
    )
    rows = result.scalars().all()

    students_result = await db.execute(select(Student).order_by(Student.created_at.asc()))
    students = students_result.scalars().all()
    student_code_map = {s.id: f"STU-{i+1:03d}" for i, s in enumerate(students)}

    return [
        {
            "id": r.id,
            "event_type": r.event_type,
            "label": EVENT_LABELS.get(r.event_type, r.event_type),
            "student_name": r.student_name,
            "student_code": student_code_map.get(r.student_id, "—") if r.student_id else "—",
            "subject": r.subject,
            "grade": r.grade,
            "input_tokens": r.input_tokens,
            "output_tokens": r.output_tokens,
            "total_tokens": r.total_tokens,
            "cost_usd": calc_cost(r.input_tokens, r.output_tokens),
            "model": r.model,
            "extra_info": r.extra_info,
            "created_at": r.created_at.isoformat(),
        }
        for r in rows
    ]