import logging
from datetime import datetime, timezone
from typing import Optional, List
import struct

from schemas import NormalizedVitals

logger = logging.getLogger(__name__)

# Contec CMS7000PLUS / CMS8000 / CMS9200PLUS OBX identifiers mapping to schema fields
CONTEC_PARAM_MAP = {
    # Heart Rate / Pulse Rate
    "HR": "heart_rate",
    "HEART_RATE": "heart_rate",
    "ECG_HR": "heart_rate",
    "PR": "heart_rate",
    "PULSE_RATE": "heart_rate",
    "SPO2_PR": "heart_rate",
    "ECGHR": "heart_rate",
    "ECG-HR": "heart_rate",
    "PULSERATE": "heart_rate",
    
    # SpO2
    "SPO2": "spo2",
    "SAO2": "spo2",
    "SPO2_PCT": "spo2",
    "OXYGEN_SAT": "spo2",
    "SPO2_VAL": "spo2",
    "O2SAT": "spo2",
    
    # Blood Pressure (NIBP)
    "NIBP_SYS": "systolic_bp",
    "NIBP_DIA": "diastolic_bp",
    "NIBP_MEAN": "map_bp",
    "NIBP_MAP": "map_bp",
    "SYS": "systolic_bp",
    "DIA": "diastolic_bp",
    "MAP": "map_bp",
    "NBP_S": "systolic_bp",
    "NBP_D": "diastolic_bp",
    "NBP_M": "map_bp",
    "NIBP-S": "systolic_bp",
    "NIBP-D": "diastolic_bp",
    "NIBP-M": "map_bp",
    "BP_SYS": "systolic_bp",
    "BP_DIA": "diastolic_bp",
    "BP_MEAN": "map_bp",
    
    # Respiratory Rate
    "RESP": "respiratory_rate",
    "RESP_RATE": "respiratory_rate",
    "RR": "respiratory_rate",
    "BR": "respiratory_rate",
    "RESPRATE": "respiratory_rate",
    "RESP-RATE": "respiratory_rate",
    
    # Temperature
    "TEMP": "temperature",
    "TEMP1": "temperature",
    "TEMP2": "temperature",
    "T1": "temperature",
    "T2": "temperature",
    "BODY_TEMP": "temperature",
    "TEMP-1": "temperature",
    "TEMP-2": "temperature",
    "BODYTEMP": "temperature",
}

# Sentinel value used by Contec to mark an invalid/disconnected parameter
INVALID_SENTINEL_U16 = 9999  # 0x270F
INVALID_SENTINEL_F32 = 9999.0


def safe_float(value: str) -> Optional[float]:
    try:
        return float(value)
    except (ValueError, TypeError):
        return None


def is_valid_u16(val: Optional[int]) -> bool:
    return val is not None and val != INVALID_SENTINEL_U16


def is_valid_f32(val: Optional[float]) -> bool:
    return val is not None and abs(val - INVALID_SENTINEL_F32) > 1.0


def read_u16_le(buf: bytes, offset: int) -> Optional[int]:
    if offset + 2 <= len(buf):
        return struct.unpack_from('<H', buf, offset)[0]
    return None


def read_f32_le(buf: bytes, offset: int) -> Optional[float]:
    if offset + 4 <= len(buf):
        return struct.unpack_from('<f', buf, offset)[0]
    return None


def parse_contec_hl7_text(raw_text: str, client_ip: str) -> Optional[NormalizedVitals]:
    """
    Lightweight, native parser for Contec HL7 messages.
    Splits segments and fields manually, avoiding third-party library dependencies.
    """
    try:
        # Strip MLLP framing if present (VT=0x0b, FS=0x1c, CR=0x0d)
        clean_text = raw_text.strip()
        if clean_text.startswith("\x0b"):
            clean_text = clean_text[1:]
        if "\x1c\x0d" in clean_text:
            clean_text = clean_text.split("\x1c\x0d")[0]
        
        # Split into segments by CR or LF
        segments = [seg.strip() for seg in clean_text.replace("\n", "\r").split("\r") if seg.strip()]
        
        if not segments or not segments[0].startswith("MSH"):
            return None

        # Parse MSH segment
        msh_fields = segments[0].split("|")
        device_id = msh_fields[2] if len(msh_fields) > 2 and msh_fields[2] else f"CMS7000_{client_ip}"
        
        patient_id = "UNKNOWN"
        vitals_dict = {
            "device_id": device_id,
            "patient_id": patient_id,
            "timestamp": datetime.now(timezone.utc),
        }
        
        found_any = False

        # Parse PID and OBX segments
        for seg in segments[1:]:
            fields = seg.split("|")
            if not fields:
                continue
                
            seg_name = fields[0]
            
            if seg_name == "PID":
                if len(fields) > 3 and fields[3]:
                    patient_id = fields[3].split("^")[0]
                    vitals_dict["patient_id"] = patient_id
                    
            elif seg_name == "OBX":
                if len(fields) > 5:
                    obs_id = fields[3].split("^")[0].strip().upper()
                    obs_val = fields[5].strip()
                    
                    if not obs_val or obs_val == "---":
                        continue
                        
                    val_float = safe_float(obs_val)
                    if val_float is None:
                        continue
                        
                    for param_key, mapped_field in CONTEC_PARAM_MAP.items():
                        if obs_id == param_key or param_key in obs_id:
                            vitals_dict[mapped_field] = val_float
                            found_any = True
                            logger.info(f"Parsed Contec HL7 Vital: {mapped_field} = {val_float} (from {obs_id})")
                            break
                            
        return NormalizedVitals(**vitals_dict) if found_any else None

    except Exception as e:
        logger.error(f"Error parsing Contec HL7 text: {e}")
        return None


def _extract_vitals_block(data: bytes, offset: int, client_ip: str) -> Optional[NormalizedVitals]:
    """
    Extract vitals from a Contec vitals block starting at the given offset.
    
    Known Contec CMS7000PLUS binary vitals block layout (confirmed from packet captures):
    
    PACKET TYPE B (header bytes [xx][00][04][46] or [xx][yy][04][46]):
    -----------------------------------------------------------------------
    Bytes 8-11   : float32 LE  → NIBP Systolic  (9999.0 = invalid)
    Bytes 12-15  : float32 LE  → NIBP Diastolic (9999.0 = invalid)
    Bytes 16-19  : float32 LE  → NIBP MAP       (9999.0 = invalid)
    Bytes 20-23  : float32 LE  → Temperature 1  (°C, 9999.0 = invalid)
    Bytes 24-27  : float32 LE  → Temperature 2  (°C, 9999.0 = invalid)
    
    Vitals summary block (at data[offset] position, found by scanning for SpO2+HR pattern):
    Offset +0    : uint16 LE   → SpO2 (%)       (9999 = invalid)
    Offset +2    : uint16 LE   → Heart Rate (bpm)(9999 = invalid, ECG not connected)
    Offset +4    : uint16 LE   → Pulse Rate (bpm)(from SpO2 probe, also 9999 if invalid)
    Offset +6    : uint16 LE   → (SpO2 alarm/threshold)
    Offset +8    : uint16 LE   → (mode flags)
    Offset +10   : uint16 LE   → NIBP Systolic  (9999 = invalid)
    Offset +12   : uint16 LE   → NIBP Diastolic (9999 = invalid)
    """
    vitals_dict = {
        "device_id": f"CMS7000PLUS_{client_ip}",
        "patient_id": "UNKNOWN",
        "timestamp": datetime.now(timezone.utc),
    }
    found = False

    spo2 = read_u16_le(data, offset)
    hr_ecg = read_u16_le(data, offset + 2)
    hr_spo2 = read_u16_le(data, offset + 4)

    # SpO2 value: valid range 50–100
    if spo2 is not None and 50 <= spo2 <= 100:
        vitals_dict["spo2"] = float(spo2)
        found = True

    # Heart rate: prefer ECG HR; fall back to SpO2-derived PR if ECG invalid
    if is_valid_u16(hr_ecg) and 20 <= hr_ecg <= 300:
        vitals_dict["heart_rate"] = float(hr_ecg)
        found = True
    elif is_valid_u16(hr_spo2) and 20 <= hr_spo2 <= 300:
        vitals_dict["heart_rate"] = float(hr_spo2)
        found = True

    return NormalizedVitals(**vitals_dict) if found else None


def _parse_float_vitals(data: bytes, base_offset: int, vitals_dict: dict) -> bool:
    """
    Parse float32 vitals (NIBP, Temperature) from packet starting at base_offset.
    Returns True if any valid vitals found.
    """
    found = False

    nibp_sys = read_f32_le(data, base_offset)
    nibp_dia = read_f32_le(data, base_offset + 4)
    nibp_map = read_f32_le(data, base_offset + 8)
    temp1 = read_f32_le(data, base_offset + 12)
    temp2 = read_f32_le(data, base_offset + 16)

    if nibp_sys is not None and is_valid_f32(nibp_sys) and 50.0 < nibp_sys < 300.0:
        vitals_dict["systolic_bp"] = round(nibp_sys, 1)
        found = True

    if nibp_dia is not None and is_valid_f32(nibp_dia) and 20.0 < nibp_dia < 200.0:
        vitals_dict["diastolic_bp"] = round(nibp_dia, 1)
        found = True

    if nibp_map is not None and is_valid_f32(nibp_map) and 20.0 < nibp_map < 250.0:
        vitals_dict["map_bp"] = round(nibp_map, 1)
        found = True

    if temp1 is not None and is_valid_f32(temp1) and 30.0 < temp1 < 45.0:
        vitals_dict["temperature"] = round(temp1, 1)
        found = True
    elif temp2 is not None and is_valid_f32(temp2) and 30.0 < temp2 < 45.0:
        vitals_dict["temperature"] = round(temp2, 1)
        found = True

    return found


def _find_vitals_block_in_stream(data: bytes, client_ip: str) -> Optional[NormalizedVitals]:
    """
    Scan the data stream for Contec CMS7000PLUS sub-packets.
    
    Contec packets follow this framing pattern:
      [len_lo] [len_hi] [04] [46] [sub_type] [00] [sub_len_lo] [00] ...payload...
    
    OR the data is a concatenation of multiple sub-packets separated by
      [xx][xx][04][47] (end marker?) 
    
    The key is to find [04][46] marker bytes and parse the packet.
    """
    vitals_dict = {
        "device_id": f"CMS7000PLUS_{client_ip}",
        "patient_id": "UNKNOWN",
        "timestamp": datetime.now(timezone.utc),
    }
    found_any = False

    # Scan through the buffer looking for [04 46] packet markers
    i = 0
    while i < len(data) - 8:
        # Look for the [04][46] marker which is the packet type indicator
        if data[i + 2] == 0x04 and data[i + 3] == 0x46:
            pkt_len = struct.unpack_from('<H', data, i)[0]  # little-endian length

            # Packet type B: small packets (< 600 bytes) with vitals summary
            # These have float32 NIBP values at offset +8 relative to packet start
            if 30 < pkt_len < 600 and i + 8 <= len(data):
                # Read float32 vitals at offsets 8, 12, 16, 20, 24 from packet start
                _parse_float_vitals(data, i + 8, vitals_dict)

                # Find the vitals summary block in this packet
                # It appears near the tail of the resp waveform data
                # The pattern we look for: SpO2 byte (50-100), followed by various u16 values
                # In packet B, the summary is 75 bytes before the end
                if pkt_len > 50:
                    # The summary block is consistently found around offset 322 in 397-byte packets
                    # Relative to packet start: around pkt_len - 75
                    summary_offset = i + max(4, pkt_len - 80)
                    if summary_offset + 10 < len(data):
                        # Scan in the last ~100 bytes of the packet for SpO2 pattern
                        scan_end = min(i + pkt_len, len(data) - 4)
                        scan_start = max(i + 4, scan_end - 100)
                        for j in range(scan_start, scan_end - 4, 2):
                            spo2 = read_u16_le(data, j)
                            hr = read_u16_le(data, j + 2)
                            pr = read_u16_le(data, j + 4)
                            
                            # Check if this looks like [SpO2][HR/sentinel][PR]
                            spo2_ok = spo2 is not None and 50 <= spo2 <= 100
                            # HR can be 9999 (invalid/ECG disconnected) or valid 20-300
                            hr_or_sentinel = hr is not None and (hr == INVALID_SENTINEL_U16 or 20 <= hr <= 300)
                            pr_ok = pr is not None and (pr == INVALID_SENTINEL_U16 or 20 <= pr <= 300)
                            
                            if spo2_ok and hr_or_sentinel and pr_ok:
                                vitals_dict["spo2"] = float(spo2)
                                found_any = True
                                
                                # Use ECG HR if valid, else use SpO2 PR
                                if hr is not None and hr != INVALID_SENTINEL_U16 and 20 <= hr <= 300:
                                    vitals_dict["heart_rate"] = float(hr)
                                elif pr is not None and pr != INVALID_SENTINEL_U16 and 20 <= pr <= 300:
                                    vitals_dict["heart_rate"] = float(pr)
                                
                                logger.info(
                                    f"Parsed vitals block at offset {j}: "
                                    f"SpO2={spo2}, HR={hr}, PR={pr}"
                                )
                                break

            # Move past this packet
            i += max(pkt_len, 4)
        else:
            i += 1

    return NormalizedVitals(**vitals_dict) if found_any else None


def parse_contec_binary_packet(data: bytes, client_ip: str) -> Optional[NormalizedVitals]:
    """
    Decodes the Contec CMS7000PLUS proprietary binary protocol.
    
    The monitor sends two alternating TCP packets:
    - Packet A (991 bytes): ECG waveform + SpO2 waveform + vitals footer  
    - Packet B (397 bytes): Resp waveform + vitals summary + param block
    
    Both have the structure: [len_lo][len_hi][04][46][subtype][00][sublen][00]...[payload]...
    """
    try:
        return _find_vitals_block_in_stream(data, client_ip)
    except Exception as e:
        logger.error(f"Error parsing Contec binary packet: {e}")
        return None


def parse_contec_data(raw_data: bytes, client_ip: str) -> Optional[NormalizedVitals]:
    """
    Unified entry point for parsing data from a Contec CMS7000PLUS monitor.
    Attempts HL7 text parsing first, falling back to proprietary binary parsing.
    """
    if not raw_data:
        return None
        
    # Attempt 1: HL7 Text Decoding
    try:
        text = raw_data.decode("utf-8", errors="ignore").strip()
        if "MSH" in text or "\x0bMSH" in text:
            vitals = parse_contec_hl7_text(text, client_ip)
            if vitals:
                return vitals
    except Exception:
        pass

    # Attempt 2: Binary Parsing (Contec proprietary protocol)
    vitals = parse_contec_binary_packet(raw_data, client_ip)
    if vitals:
        return vitals

    # Logging fallback
    logger.warning(
        f"Data packet from {client_ip} unrecognized. "
        f"Len: {len(raw_data)}, Hex head: {raw_data[:32].hex()}"
    )
    return None