"""Signal API — FastAPI backend for CSV ingestion, scoring, and export."""

import csv
import hashlib
import io
import os
import sys
from datetime import date, date as date_type
from functools import lru_cache
from pathlib import Path
from typing import Optional

import jwt
from jwt import PyJWKClient, ExpiredSignatureError, InvalidTokenError
from fastapi import Depends, FastAPI, File, Header, HTTPException, UploadFile
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import StreamingResponse
from pydantic import BaseModel

# Ensure python-backend root is on path (works both locally and in Docker)
_backend_root = Path(__file__).parent.parent
if str(_backend_root) not in sys.path:
    sys.path.insert(0, str(_backend_root))

from core.coverage_calculator import ShipmentRecord, calculate_batch
from core.audit_logger import AuditAction, log_event
from core.doc_state_machine import compute_doc_state, DocState
from core.persistence import (
    persist_export, persist_upload,
    upsert_confirmed_visit, load_confirmed_visits_for_org, get_or_create_org,
)
from api.normalizer import normalize_csv

app = FastAPI(title="Signal API", version="1.0.0", docs_url="/docs")

# CORS — locked to Vercel frontend and localhost for dev.
# Set ALLOWED_ORIGINS in Railway as a comma-separated list for production.
_origins_env = os.getenv("ALLOWED_ORIGINS", "")
_allowed_origins: list[str] = (
    [o.strip() for o in _origins_env.split(",") if o.strip()]
    if _origins_env
    else [
        "http://localhost:5173",
        "http://localhost:5174",
        "http://127.0.0.1:5173",
    ]
)

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

# API key auth — enforced when SIGNAL_API_KEY env var is set.
# In dev (no env var), all requests pass. In production, X-API-Key header is required.
_api_key = os.getenv("SIGNAL_API_KEY", "")
_clerk_jwks_url = os.getenv("CLERK_JWKS_URL", "")


@lru_cache(maxsize=1)
def _get_jwks_client() -> PyJWKClient:
    if not _clerk_jwks_url:
        raise RuntimeError("CLERK_JWKS_URL is not set")
    return PyJWKClient(_clerk_jwks_url, cache_keys=True, cache_jwk_set=True, lifespan=300)


def verify_clerk_token(authorization: str) -> dict:
    """Verify a Clerk Bearer JWT. Returns decoded claims or raises HTTP 401."""
    if not authorization.startswith("Bearer "):
        raise HTTPException(status_code=401, detail="Missing or malformed Authorization header")
    token = authorization.removeprefix("Bearer ").strip()
    try:
        client = _get_jwks_client()
        signing_key = client.get_signing_key_from_jwt(token)
        return jwt.decode(token, signing_key.key, algorithms=["RS256"],
                          options={"verify_exp": True, "verify_nbf": True})
    except ExpiredSignatureError:
        raise HTTPException(status_code=401, detail="Token has expired")
    except InvalidTokenError as exc:
        raise HTTPException(status_code=401, detail=f"Invalid token: {exc}")
    except RuntimeError:
        raise HTTPException(status_code=503, detail="Auth service not configured")
    except Exception:
        raise HTTPException(status_code=401, detail="Token verification failed")


def require_auth(
    authorization: str = Header(default=""),
    x_api_key: str = Header(default=""),
) -> dict:
    """
    Accept either a Clerk JWT (Authorization: Bearer) or a direct API key (X-Api-Key).
    Returns a claims dict. API-key path returns a synthetic service-account dict.
    """
    # Fast path: API key (for direct access / testing)
    if _api_key and x_api_key == _api_key:
        return {"sub": "service-account", "via": "api_key"}
    # Clerk JWT path (frontend / production)
    if authorization.startswith("Bearer "):
        return verify_clerk_token(authorization)
    # Dev mode: no keys set — allow all
    if not _api_key and not _clerk_jwks_url:
        return {"sub": "dev", "via": "open"}
    raise HTTPException(status_code=401, detail="Authentication required")

DEVICE_DISPLAY = {
    "dexcom_g7": "Dexcom G7",
    "dexcom_g6": "Dexcom G6",
    "freestyle_libre_2": "FreeStyle Libre 2",
    "freestyle_libre_3": "FreeStyle Libre 3",
    "omnipod_5": "Omnipod 5",
}

FLAG_LABELS = {
    "SUPPLY_LAPSED":    "Supply Lapsed",
    "VISIT_REQUIRED":   "Visit Required",
    "TRANSFER_PENDING": "Needs Verification — Transfer",
    "RENEWAL_CRITICAL": "Renewal Due — Critical",
    "RENEWAL_ELEVATED": "Renewal Due SOON",
    "RENEWAL_SOON":     "Renewal Due SOON",
    "RESUPPLY_READY":   "Resupply Ready",
    "ACTIVE":           "Active",
}

FLAG_ACTIONS = {
    "SUPPLY_LAPSED":    "Contact Prescriber — Supply Lapsed",
    "VISIT_REQUIRED":   "Contact Prescriber — Visit Overdue",
    "TRANSFER_PENDING": "Verify All Documentation",
    "RENEWAL_CRITICAL": "Contact Prescriber — Confirm Visit Appointment",
    "RENEWAL_ELEVATED": "Contact Prescriber — Schedule Qualifying Visit",
    "RENEWAL_SOON":     "Monitor — Visit Due in 90 Days",
    "RESUPPLY_READY":   "Initiate Resupply",
    "ACTIVE":           "No action needed",
}


class DocStateOut(BaseModel):
    swo: str
    visit: str
    pecos: str
    pa: str
    diagnosis: str


class RecordOut(BaseModel):
    patient_id: str
    device_type: str
    device_display: str
    payer: str
    component: str
    days_until_coverage_end: int
    days_until_visit_due: Optional[int] = None
    flag: str
    priority_score: int
    coverage_end_date: str
    next_visit_due_date: Optional[str] = None
    action: str
    status_label: str
    reason: str
    rule_version: str
    visit_date_confidence: str = "estimated"
    is_transfer: bool = False
    doc_state: Optional[DocStateOut] = None
    cascade: list[str] = []


class UploadResponse(BaseModel):
    records: list[RecordOut]
    total: int
    skipped: int
    skipped_reasons: list[str]
    stats: dict
    mapping_summary: dict
    batch_id: Optional[str] = None


def _build_reason(flag_val: str, days_until_end: int, days_until_visit: Optional[int]) -> str:
    if flag_val == "SUPPLY_LAPSED":
        ago = abs(days_until_end)
        unit = "day" if ago == 1 else "days"
        return f"Supply lapsed {ago} {unit} ago. Prescriber contact required before next shipment."
    if flag_val == "VISIT_REQUIRED":
        if days_until_visit is not None and days_until_visit <= 0:
            overdue = abs(days_until_visit)
            unit = "day" if overdue == 1 else "days"
            return f"Qualifying visit overdue by {overdue} {unit}. Confirm documentation immediately."
        return "Qualifying visit renewal required. Confirm documentation before resupply."
    if flag_val == "RENEWAL_CRITICAL":
        if days_until_visit is not None:
            unit = "day" if days_until_visit == 1 else "days"
            return f"Qualifying visit due in {days_until_visit} {unit}. Contact prescriber immediately."
        return "Qualifying visit renewal critical. Confirm visit documentation before resupply."
    if flag_val == "RENEWAL_ELEVATED":
        if days_until_visit is not None:
            unit = "day" if days_until_visit == 1 else "days"
            return f"Qualifying visit due in {days_until_visit} {unit}. Schedule prescriber appointment soon."
        return "Qualifying visit renewal elevated. Schedule prescriber appointment."
    if flag_val == "RENEWAL_SOON":
        if days_until_visit is not None:
            unit = "day" if days_until_visit == 1 else "days"
            return f"Qualifying visit due in {days_until_visit} {unit}. Monitor and plan ahead."
        return "Qualifying visit renewal approaching. Monitor status."
    if flag_val == "RESUPPLY_READY":
        unit = "day" if days_until_end == 1 else "days"
        return f"Coverage ends in {days_until_end} {unit}. Patient is within resupply window — initiate shipment now."
    if flag_val == "TRANSFER_PENDING":
        return "Patient transferred from prior supplier. Verify all documentation before proceeding."
    unit = "day" if days_until_end == 1 else "days"
    return f"Coverage on track. Resupply window opens in approximately {days_until_end} {unit}."


def _normalize_payer_type(payer: str) -> str:
    """Map raw payer string to doc_state_machine payer_type."""
    from core.coverage_calculator import _normalize_payer
    normalized = _normalize_payer(payer)
    # Ensure medicare_advantage is not collapsed to medicare
    if "medicare advantage" in payer.lower() or "medicare_advantage" in payer.lower():
        return "medicare_advantage"
    return normalized


def _to_record_out(r, record=None) -> RecordOut:
    flag_val = r.flag.value if hasattr(r.flag, "value") else str(r.flag)

    # Compute doc state if we have the original record
    doc_state_out = None
    cascade = []
    if record is not None:
        normalized_payer = _normalize_payer_type(r.payer)
        doc = compute_doc_state(
            payer_type=normalized_payer,
            csv_swo_status=record.csv_swo_status,
            csv_visit_date=record.csv_visit_date,
            confirmed_visit_date=None,  # already factored into r.next_visit_due_date
            csv_pecos_verified=record.csv_pecos_verified,
            csv_pa_status=record.csv_pa_status,
            csv_diagnosis_on_file=record.csv_diagnosis_on_file,
            is_transfer=bool(record.csv_transfer_from),
        )
        doc_state_out = DocStateOut(
            swo=doc.swo, visit=doc.visit, pecos=doc.pecos, pa=doc.pa, diagnosis=doc.diagnosis
        )
        cascade = doc.cascade

    return RecordOut(
        patient_id=r.patient_id,
        device_type=r.device_type,
        device_display=DEVICE_DISPLAY.get(r.device_type, r.device_type),
        payer=r.payer,
        component=r.component,
        days_until_coverage_end=r.days_until_coverage_end,
        days_until_visit_due=r.days_until_visit_due,
        flag=flag_val,
        priority_score=r.priority_score,
        coverage_end_date=r.coverage_end_date.isoformat(),
        next_visit_due_date=r.next_visit_due_date.isoformat() if r.next_visit_due_date else None,
        action=FLAG_ACTIONS.get(flag_val, "Review"),
        status_label=FLAG_LABELS.get(flag_val, flag_val),
        reason=_build_reason(flag_val, r.days_until_coverage_end, r.days_until_visit_due),
        rule_version=r.rule_version,
        visit_date_confidence=getattr(r, "visit_date_confidence", "estimated"),
        is_transfer=getattr(r, "is_transfer", False),
        doc_state=doc_state_out,
        cascade=cascade,
    )


def _compute_stats(records: list[RecordOut]) -> dict:
    flags = [r.flag for r in records]
    return {
        "total": len(records),
        "supply_lapsed": flags.count("SUPPLY_LAPSED"),
        "visit_required": flags.count("VISIT_REQUIRED"),
        "transfer_pending": flags.count("TRANSFER_PENDING"),
        "renewal_critical": flags.count("RENEWAL_CRITICAL"),
        "renewal_elevated": flags.count("RENEWAL_ELEVATED"),
        "renewal_soon": flags.count("RENEWAL_SOON"),
        "resupply_ready": flags.count("RESUPPLY_READY"),
        "active": flags.count("ACTIVE"),
        "prescriber_action": (
            flags.count("SUPPLY_LAPSED") + flags.count("VISIT_REQUIRED") +
            flags.count("RENEWAL_CRITICAL") + flags.count("RENEWAL_ELEVATED")
        ),
    }


@app.get("/health")
def health():
    return {"status": "ok", "service": "signal-api", "version": "1.0.0"}


@app.get("/health/db")
def health_db():
    from core.supabase_client import get_client
    import os
    client = get_client()
    if not client:
        return {
            "status": "unavailable",
            "supabase_url_set": bool(os.getenv("SUPABASE_URL")),
            "service_key_set": bool(os.getenv("SUPABASE_SERVICE_KEY")),
        }
    try:
        result = client.table("organizations").select("id").limit(1).execute()
        return {"status": "ok", "org_count": len(result.data)}
    except Exception as e:
        return {"status": "error", "detail": str(e)}


@app.post("/api/upload", response_model=UploadResponse)
async def upload_csv(
    file: UploadFile = File(...),
    claims: dict = Depends(require_auth),
):
    if not (file.filename or "").endswith(".csv"):
        raise HTTPException(status_code=400, detail="File must be a .csv")

    content = await file.read()
    try:
        text = content.decode("utf-8")
    except UnicodeDecodeError:
        text = content.decode("latin-1")

    records, skipped_reasons, mapping_summary = normalize_csv(text)

    if not records:
        log_event(AuditAction.CSV_INGEST, file.filename or "unknown", "demo_user",
                  "failure", "0.0.0.0", detail="No processable rows")
        raise HTTPException(
            status_code=422,
            detail={
                "message": "No processable rows found in the uploaded file.",
                "skipped": skipped_reasons[:10],
                "mapping_summary": mapping_summary,
            },
        )

    # Load confirmed visit dates from Supabase for this org
    clerk_org_id = claims.get("o", {}).get("id") if isinstance(claims.get("o"), dict) else None
    org_id = get_or_create_org(clerk_org_id=clerk_org_id)
    confirmed_visits = load_confirmed_visits_for_org(org_id) if org_id else {}

    results = calculate_batch(records, as_of=date.today(), confirmed_visits=confirmed_visits)

    # Build a lookup from patient_id to original record for doc state computation
    record_lookup = {r.patient_id: r for r in records}
    out = [_to_record_out(r, record=record_lookup.get(r.patient_id)) for r in results]

    log_event(AuditAction.CSV_INGEST, file.filename or "unknown", "demo_user",
              "success", "0.0.0.0", detail=f"{len(out)} records scored")

    batch_id = persist_upload(
        filename=file.filename or "unknown",
        content_bytes=content,
        shipment_records=records,
        coverage_results=results,
        skipped_count=len(skipped_reasons),
        mapping_summary=mapping_summary,
        clerk_org_id=clerk_org_id,
    )

    return UploadResponse(
        records=out,
        total=len(out),
        skipped=len(skipped_reasons),
        skipped_reasons=skipped_reasons[:20],
        stats=_compute_stats(out),
        mapping_summary=mapping_summary,
        batch_id=batch_id,
    )


class ExportRequest(BaseModel):
    records: list[RecordOut]
    batch_id: Optional[str] = None


@app.post("/api/export")
async def export_work_queue(
    body: ExportRequest,
    claims: dict = Depends(require_auth),
):
    """Generate a downloadable work-queue CSV from a list of scored records."""
    records = body.records
    output = io.StringIO()
    writer = csv.writer(output)
    writer.writerow([
        "Patient ID",
        "Device",
        "Payer",
        "Status",
        "Priority Score",
        "Days Until Resupply End",
        "Next Visit Due",
        "Recommended Action",
        "Resupply End Date",
        "Reason",
        "Visit Confidence",
        "SWO Status",
        "Visit Status",
        "PA Status",
    ])
    for r in records:
        doc = r.doc_state
        writer.writerow([
            r.patient_id,
            r.device_display,
            r.payer,
            r.status_label,
            r.priority_score,
            r.days_until_coverage_end,
            r.next_visit_due_date or "",
            r.action,
            r.coverage_end_date,
            r.reason,
            r.visit_date_confidence,
            doc.swo if doc else "",
            doc.visit if doc else "",
            doc.pa if doc else "",
        ])

    output.seek(0)
    today = date.today().isoformat()
    export_filename = f"signal-work-queue-{today}.csv"
    log_event(AuditAction.WORKLIST_EXPORT, export_filename, "demo_user",
              "success", "0.0.0.0", detail=f"{len(records)} records exported")
    persist_export(batch_id=body.batch_id, filename=export_filename, row_count=len(records))
    return StreamingResponse(
        io.BytesIO(output.getvalue().encode("utf-8")),
        media_type="text/csv",
        headers={
            "Content-Disposition": f"attachment; filename=signal-work-queue-{today}.csv"
        },
    )


class ConfirmVisitRequest(BaseModel):
    patient_id: str
    confirmed_date: str  # ISO date string YYYY-MM-DD
    # Fields needed to recompute coverage after confirmation
    shipment_date: str
    payer: str
    device_type: str
    quantity: int = 1
    component: str = "sensor"


@app.post("/api/confirm-visit")
async def confirm_visit(
    body: ConfirmVisitRequest,
    claims: dict = Depends(require_auth),
):
    """
    Store a staff-confirmed qualifying visit date and return the updated coverage record.
    The confirmed date persists across all future CSV imports for this patient_id.
    """
    from core.coverage_calculator import ShipmentRecord, calculate_coverage

    # Validate dates
    try:
        confirmed = date_type.fromisoformat(body.confirmed_date)
        shipment = date_type.fromisoformat(body.shipment_date)
    except ValueError as e:
        raise HTTPException(status_code=400, detail=f"Invalid date: {e}. Use YYYY-MM-DD.")

    if confirmed > date_type.today():
        raise HTTPException(status_code=400, detail="Confirmed date cannot be in the future.")

    # Get org
    clerk_org_id = claims.get("o", {}).get("id") if isinstance(claims.get("o"), dict) else None
    org_id = get_or_create_org(clerk_org_id=clerk_org_id)
    if not org_id:
        raise HTTPException(status_code=503, detail="Organization not found.")

    # Hash and store
    patient_hash = hashlib.sha256(body.patient_id.encode()).hexdigest()
    success = upsert_confirmed_visit(org_id, patient_hash, confirmed, confirmed_by="staff")
    if not success:
        raise HTTPException(status_code=503, detail="Failed to save confirmed visit.")

    # Recompute coverage with confirmed visit date
    record = ShipmentRecord(
        patient_id=body.patient_id,
        device_type=body.device_type,
        shipment_date=shipment,
        quantity=body.quantity,
        payer=body.payer,
        component=body.component,
    )
    result = calculate_coverage(record, confirmed_visit_date=confirmed)

    log_event(
        AuditAction.CSV_INGEST,
        f"confirm-visit:{body.patient_id[:8]}",
        "staff",
        "success",
        "0.0.0.0",
        detail=f"Visit confirmed {confirmed.isoformat()}",
    )

    return _to_record_out(result, record=record)