"""
GLADIUS v2.0 — Time Engine

Dual-clock temporal encoding:
  Absolute Clock: Time2Vec — wall-clock time as learned periodic functions.
  Relative Clock: Event-anchored with exponential decay.

Injected ADDITIVELY into hidden states (like a bias), not concatenated.
Does not interfere with RoPE (rotational) — operates in different subspace.

argmax_memory S(relevance | query, time_decay) — time modulates every scoring function.
"""

import torch
import torch.nn as nn
import math
import time as time_module

from .config import KernelConfig


class AbsoluteClock(nn.Module):
    """
    Time2Vec: learned periodic encoding of wall-clock time.

    Input: scalar timestamp (seconds since epoch)
    Output: vector of learned periodic features

    t → [ω₁t + φ₁, sin(ω₂t + φ₂), sin(ω₃t + φ₃), ...]
    First component is linear (trend), rest are periodic (patterns).
    """

    def __init__(self, num_frequencies: int = 16):
        super().__init__()
        self.num_frequencies = num_frequencies

        # Learnable frequency and phase for each component
        self.omega = nn.Parameter(torch.randn(num_frequencies) * 0.01)
        self.phi = nn.Parameter(torch.zeros(num_frequencies))

    def forward(self, timestamp: torch.Tensor) -> torch.Tensor:
        """
        Args:
            timestamp: (batch,) — seconds since epoch, normalized
        Returns:
            encoding: (batch, num_frequencies)
        """
        # Normalize timestamp to reasonable range
        t = timestamp.unsqueeze(-1)  # (B, 1)

        # First component: linear (captures trend)
        linear = self.omega[0:1] * t + self.phi[0:1]

        # Remaining: periodic (captures patterns — daily, weekly, etc.)
        periodic = torch.sin(self.omega[1:] * t + self.phi[1:])

        return torch.cat([linear, periodic], dim=-1)  # (B, num_frequencies)


class RelativeClock(nn.Module):
    """
    Event-anchored temporal encoding with exponential decay.

    Tracks recent events and encodes "time since event X" with decay.
    Recent events have strong encoding, old events fade.

    This gives GLADIUS a sense of "how long ago" something happened.
    """

    def __init__(self, config: KernelConfig):
        super().__init__()
        self.max_events = config.time_max_events
        self.num_frequencies = config.time_num_frequencies

        # Event buffer (not a parameter — updated at runtime)
        self.register_buffer('event_times', torch.zeros(config.time_max_events))
        self.register_buffer('event_head', torch.tensor(0, dtype=torch.long))

        # Learned decay rates per frequency
        self.decay = nn.Parameter(torch.ones(config.time_num_frequencies) * 0.01)

        # Projection from event features to encoding
        self.proj = nn.Linear(config.time_max_events, config.time_num_frequencies, bias=False)

    def record_event(self, timestamp: float):
        """Record a new event timestamp."""
        with torch.no_grad():
            idx = self.event_head.item() % self.max_events
            self.event_times[idx] = timestamp
            self.event_head += 1

    def forward(self, current_time: torch.Tensor) -> torch.Tensor:
        """
        Args:
            current_time: (batch,) — current timestamp
        Returns:
            encoding: (batch, num_frequencies)
        """
        # Time since each event
        deltas = current_time.unsqueeze(-1) - self.event_times.unsqueeze(0)  # (B, max_events)
        deltas = deltas.clamp(min=0)  # No future events

        # Exponential decay
        # log-scale the deltas to handle large time ranges
        log_deltas = torch.log1p(deltas)  # log(1 + delta) for numerical stability

        # Decay-weighted features
        decayed = torch.exp(-self.decay.abs().unsqueeze(0) * self.proj(log_deltas))

        return decayed  # (B, num_frequencies)


class TemporalFusion(nn.Module):
    """
    Fuses absolute + relative clock into a single temporal embedding.
    Projects to hidden_dim for additive injection.
    """

    def __init__(self, config: KernelConfig):
        super().__init__()
        input_dim = config.time_num_frequencies * 2  # absolute + relative
        self.proj = nn.Sequential(
            nn.Linear(input_dim, config.time_dim),
            nn.SiLU(),
            nn.Linear(config.time_dim, config.hidden_dim),
        )

    def forward(self, absolute: torch.Tensor, relative: torch.Tensor) -> torch.Tensor:
        """
        Args:
            absolute: (batch, num_frequencies)
            relative: (batch, num_frequencies)
        Returns:
            temporal_embedding: (batch, hidden_dim)
        """
        combined = torch.cat([absolute, relative], dim=-1)
        return self.proj(combined)


class TimeEngine(nn.Module):
    """
    Complete time engine. Produces temporal embeddings for additive injection.

    Supports two modes:
      - 'continuous' (default): Time2Vec — learned periodic functions
      - 'lattice': LatticeClock — discrete quantized positions

    Usage:
        time_embed = time_engine(timestamp)  # (B, hidden_dim)
        hidden = hidden + time_embed.unsqueeze(1)  # Broadcast across seq_len
    """

    def __init__(self, config: KernelConfig):
        super().__init__()
        
        # Determine clock mode from config
        self.clock_mode = getattr(config, 'clock_mode', 'continuous')
        
        if self.clock_mode == 'lattice':
            from .temporal_lattice import LatticeClock
            self.lattice = LatticeClock(config)
        else:
            self.absolute = AbsoluteClock(config.time_num_frequencies)
            self.fusion = TemporalFusion(config)
        
        # Relative clock is used in both modes
        self.relative = RelativeClock(config)

        # Normalization factor for timestamps (seconds since 2026-01-01)
        self.register_buffer('epoch_offset', torch.tensor(1735689600.0))  # 2026-01-01 UTC

    def normalize_timestamp(self, timestamp: torch.Tensor) -> torch.Tensor:
        """Normalize to reasonable range for learned frequencies."""
        # Convert to hours since epoch_offset (ensure device alignment)
        epoch = self.epoch_offset.to(timestamp.device)
        return (timestamp - epoch) / 3600.0

    def forward(self, timestamp: torch.Tensor | float | None = None) -> torch.Tensor:
        """
        Args:
            timestamp: (batch,) seconds since Unix epoch, or None for current time
        Returns:
            temporal_embedding: (batch, hidden_dim)
        """
        if timestamp is None:
            timestamp = torch.tensor([time_module.time()])
        if isinstance(timestamp, (int, float)):
            timestamp = torch.tensor([timestamp], dtype=torch.float32)
        # Ensure timestamp is on same device as model parameters
        target_device = next(self.parameters()).device
        timestamp = timestamp.to(target_device)

        t_norm = self.normalize_timestamp(timestamp)
        
        if self.clock_mode == 'lattice':
            # Lattice mode: discrete quantized temporal encoding
            return self.lattice(t_norm)
        else:
            # Continuous mode: Time2Vec + RelativeClock fusion
            abs_enc = self.absolute(t_norm)
            rel_enc = self.relative(timestamp)
            return self.fusion(abs_enc, rel_enc)

    def record_event(self, timestamp: float | None = None):
        """Record an event in the relative clock."""
        if timestamp is None:
            timestamp = time_module.time()
        self.relative.record_event(timestamp)