"""
api/main.py
REST API Service for HIFFI Hip-Hop 500 Multi-Platform Intelligence.
Secured with header-based auth secret (X-Auth-Secret).
"""

import os
from pathlib import Path
import sys
from typing import Optional

from dotenv import load_dotenv
from fastapi import FastAPI, Header, HTTPException, Query, Security, status
from fastapi.middleware.cors import CORSMiddleware
import pandas as pd

PROJECT_ROOT = Path(__file__).resolve().parent.parent
if str(PROJECT_ROOT) not in sys.path:
    sys.path.insert(0, str(PROJECT_ROOT))

load_dotenv(PROJECT_ROOT / ".env")

AUTH_SECRET = os.getenv("AUTH_SECRET", "hiffi_live_secret_key_prod_2026").strip()
DATA_FILE = PROJECT_ROOT / "data" / "hiffi_multiplatform_500.csv"

app = FastAPI(
    title="HIFFI Artist Intelligence API",
    version="1.0.0",
    description="Programmatic query and ranking endpoints for the HIFFI Hip-Hop 500 cohort.",
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


def verify_auth_secret(x_auth_secret: Optional[str] = Header(None)):
    """Validates the auth secret passed in the request header."""
    if not x_auth_secret or x_auth_secret != AUTH_SECRET:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Unauthorized: Invalid or missing X-Auth-Secret header.",
        )
    return x_auth_secret


def get_dataset() -> pd.DataFrame:
    """Loads the current master cohort dataset."""
    if not DATA_FILE.exists():
        raise HTTPException(
            status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
            detail="Cohort dataset not found. Please run run_pipeline.py first.",
        )
    return pd.read_csv(DATA_FILE)


@app.get("/health", tags=["System"])
def health_check():
    """Public health probe."""
    return {"status": "HEALTHY", "dataset_exists": DATA_FILE.exists()}


@app.get("/api/v1/cohort", tags=["Rankings"])
def get_cohort_rankings(
    tier: Optional[int] = Query(None, ge=0, le=3, description="Filter by platform evidence tier (0-3)"),
    limit: int = Query(50, ge=1, le=500, description="Max records to return"),
    offset: int = Query(0, ge=0, description="Offset for pagination"),
    auth: str = Security(verify_auth_secret),
):
    """Fetches published cohort rankings with pagination and tier filtering."""
    df = get_dataset()

    if tier is not None and "platform_evidence_tier" in df.columns:
        df = df[df["platform_evidence_tier"] == tier]

    if "hiffi_xp_published_rank" in df.columns:
        df = df.sort_values(by="hiffi_xp_published_rank", ascending=True)

    paginated = df.iloc[offset : offset + limit]
    
    # Safe replacement of NaN/inf with None for valid JSON serialization
    clean_df = paginated.replace({float('nan'): None, float('inf'): None, float('-inf'): None})
    records = clean_df.to_dict(orient="records")

    return {
        "total": len(df),
        "limit": limit,
        "offset": offset,
        "results": records,
    }

@app.get("/api/v1/artists/{artist_name}", tags=["Artists"])
def get_artist_dossier(
    artist_name: str,
    auth: str = Security(verify_auth_secret),
):
    """Retrieves full telemetry, evidence tiers, and ranks for a single artist."""
    df = get_dataset()
    match = df[df["name"].str.strip().str.lower() == artist_name.strip().lower()]

    if match.empty:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND,
            detail=f"Artist '{artist_name}' not found in cohort.",
        )

    row = match.iloc[0].where(pd.notna(match.iloc[0]), None).to_dict()
    return {"status": "SUCCESS", "artist": row}


@app.post("/api/v1/pipeline/run", tags=["Pipeline"])
def trigger_pipeline_run(auth: str = Security(verify_auth_secret)):
    """Triggers deterministic re-scoring, anomaly detection, and publication gating."""
    from core.ranking_engine import HIFFIRankingEngine

    df = get_dataset()
    engine = HIFFIRankingEngine()

    scored = engine.calculate_hiffi_xp(df)
    flagged = engine.detect_metric_anomalies(scored)
    gated, audit = engine.apply_publication_eligibility_gates(flagged, return_metadata=True)

    gated.to_csv(DATA_FILE, index=False)

    return {
        "status": "SUCCESS",
        "message": "Pipeline recalculated and dataset refreshed.",
        "shortfall_audit": audit,
    }