app/services/analytics/amazon_fees.py

"""Amazon US marketplace fee formulas (Seller Central Revenue Calculator aligned).

Sources: Amazon Seller Central fee schedule (FBA fulfillment, referral, storage,
inbound placement). Rates reflect 2024–2025 US standard-size tiers.
"""
from __future__ import annotations

from dataclasses import dataclass
from typing import Dict, Literal, Optional, Tuple

Season = Literal["standard", "peak"]

# Referral fee % by category keyword (Amazon US published rates)
REFERRAL_RATES: Dict[str, float] = {
    "amazon device": 0.45,
    "apparel": 0.17,
    "clothing": 0.17,
    "shoe": 0.15,
    "jewelry": 0.20,
    "electronics": 0.08,
    "computer": 0.08,
    "camera": 0.08,
    "cell phone": 0.08,
    "cell phones": 0.08,
    "phone": 0.08,
    "wireless": 0.08,
    "tablet": 0.08,
    "beauty": 0.08,
    "personal care": 0.08,
    "health": 0.08,
    "grocery": 0.08,
    "baby": 0.08,
    "book": 0.15,
    "music": 0.15,
    "video": 0.15,
    "software": 0.15,
    "video game": 0.15,
    "game console": 0.08,
    "toy": 0.15,
    "home": 0.15,
    "kitchen": 0.15,
    "garden": 0.15,
    "tool": 0.15,
    "sport": 0.15,
    "outdoor": 0.15,
    "pet": 0.15,
    "office": 0.15,
    "industrial": 0.12,
    "automotive": 0.12,
    "default": 0.15,
}

REFERRAL_MIN = 0.30

# 3.5% fuel & logistics surcharge on FBA fulfillment (US/CA, from Apr 2026)
FULFILLMENT_LOGISTICS_SURCHARGE = 1.035

# FBA US fulfillment — large standard non-apparel (2025–2026 US, before surcharge in table)
# Weight in oz → fee USD (small standard ≤16 oz, large standard ≤20 lb)
SMALL_STANDARD_OZ: Tuple[Tuple[float, float], ...] = (
    (2, 3.06),
    (4, 3.15),
    (6, 3.24),
    (8, 3.33),
    (10, 3.43),
    (12, 3.53),
    (14, 3.60),
    (16, 3.65),
)

LARGE_STANDARD_LBS: Tuple[Tuple[float, float], ...] = (
    (0.25, 4.99),
    (0.5, 5.28),
    (0.75, 5.48),
    (1.0, 5.93),
    (1.25, 6.38),
    (1.5, 6.62),
    (1.75, 6.98),
    (2.0, 7.20),
    (2.25, 7.46),
    (2.5, 7.72),
    (2.75, 7.95),
    (3.0, 8.38),
    (20.0, 11.90),
)

# Storage $/cu ft per month (standard-size)
STORAGE_RATE_CUFT: Dict[Season, float] = {
    "standard": 0.87,  # Jan–Sep
    "peak": 2.40,      # Oct–Dec
}

# Default unit volume when dimensions unknown (typical small standard ~0.05 cu ft)
DEFAULT_CU_FT_PER_UNIT = 0.05

# Inbound placement service fee per unit (US) — applied when seller enters inbound shipping
INBOUND_PLACEMENT_DEFAULT = 0.56

INBOUND_BY_REGION = {
    "west": 0.56,
    "central": 0.48,
    "east": 0.52,
}

REMOVAL_FEE_PER_UNIT = 3.95
DISPOSAL_FEE_PER_UNIT = 3.95


def calculate_removal_disposal_cost(
    removal_units: int = 0,
    disposal_units: int = 0,
    monthly_units_sold: float = 1.0,
) -> Dict:
    total = round(removal_units * REMOVAL_FEE_PER_UNIT + disposal_units * DISPOSAL_FEE_PER_UNIT, 2)
    per_unit = round(total / max(monthly_units_sold, 1), 2) if total else 0.0
    return {
        "removal_fee_per_unit": REMOVAL_FEE_PER_UNIT,
        "disposal_fee_per_unit": DISPOSAL_FEE_PER_UNIT,
        "removal_units": removal_units,
        "disposal_units": disposal_units,
        "total_removal_disposal_fee": total,
        "removal_disposal_cost_per_unit_sold": per_unit,
    }


@dataclass
class ProductDimensions:
    weight_lbs: float = 1.0
    length_in: float = 10.0
    width_in: float = 8.0
    height_in: float = 2.0

    @property
    def weight_oz(self) -> float:
        return self.weight_lbs * 16

    @property
    def cubic_feet(self) -> float:
        return max((self.length_in * self.width_in * self.height_in) / 1728, 0.001)


def resolve_referral_rate(category: str) -> Tuple[float, str]:
    cat = (category or "").lower()
    # Cell phones & accessories → 8% (must check before generic "accessories")
    if "cell phone" in cat or "cell phones" in cat or ("phone" in cat and "accessories" in cat):
        return 0.08, "cell phones"
    for key, rate in REFERRAL_RATES.items():
        if key != "default" and key in cat:
            return rate, key
    return REFERRAL_RATES["default"], "default"


def _uses_large_standard(dims: ProductDimensions, category: str = "") -> bool:
    """Phones and many electronics ship in large-standard boxes even under 1 lb."""
    cat = (category or "").lower()
    if any(k in cat for k in ("cell phone", "phone", "tablet", "electronics", "computer")):
        return True
    longest = max(dims.length_in, dims.width_in, dims.height_in)
    median = sorted([dims.length_in, dims.width_in, dims.height_in])[1]
    if longest > 15 or median > 12 or dims.weight_lbs > 1.0:
        return True
    return dims.weight_lbs * 16 > 16


def calculate_fba_fulfillment_fee(weight_lbs: float, dims: Optional[ProductDimensions] = None, category: str = "") -> Dict:
    """Return FBA pick-pack-ship fee from weight/size tier + 3.5% logistics surcharge."""
    if dims is None:
        dims = estimate_dimensions_from_weight(weight_lbs, category)
    weight_lbs = max(weight_lbs, dims.weight_lbs)
    weight_oz = weight_lbs * 16
    use_large = _uses_large_standard(dims, category)
    fee = 11.90
    tier = "large_standard" if use_large else "small_standard"

    if not use_large and weight_oz <= 16:
        for max_oz, tier_fee in SMALL_STANDARD_OZ:
            if weight_oz <= max_oz:
                fee = tier_fee
                break
    else:
        tier = "large_standard"
        for max_lbs, tier_fee in LARGE_STANDARD_LBS:
            if weight_lbs <= max_lbs:
                fee = tier_fee
                break

    base_fee = round(fee, 2)
    total_fee = round(base_fee * FULFILLMENT_LOGISTICS_SURCHARGE, 2)

    return {
        "fba_fulfillment_fee": total_fee,
        "fba_fulfillment_fee_base": base_fee,
        "fulfillment_surcharge_percent": 3.5,
        "fulfillment_tier": tier,
        "weight_lbs": round(weight_lbs, 3),
        "weight_oz": round(weight_oz, 1),
    }


def calculate_referral_fee(price: float, category: str = "default") -> Dict:
    rate, matched = resolve_referral_rate(category)
    fee = round(max(price * rate, REFERRAL_MIN), 2)
    return {
        "referral_fee": fee,
        "referral_rate_percent": round(rate * 100, 1),
        "referral_category": matched,
        "fixed_closing_fee": 0.0,
        "variable_closing_fee": 0.0,
        "digital_services_fee": 0.0,
    }


def calculate_storage_fee_per_unit(
    dims: ProductDimensions,
    season: Season = "standard",
    avg_inventory_units: float = 1.0,
    monthly_units_sold: float = 1.0,
) -> Dict:
    monthly_per_cuft = STORAGE_RATE_CUFT[season]
    monthly_per_unit = round(dims.cubic_feet * monthly_per_cuft, 4)
    if monthly_units_sold <= 0:
        per_unit_sold = 0.0
    else:
        per_unit_sold = round((monthly_per_unit * max(avg_inventory_units, 0)) / monthly_units_sold, 2)
    return {
        "season": season,
        "cubic_feet_per_unit": round(dims.cubic_feet, 4),
        "monthly_storage_rate_per_cuft": monthly_per_cuft,
        "monthly_storage_cost_per_unit": monthly_per_unit,
        "avg_inventory_units": avg_inventory_units,
        "monthly_units_sold": monthly_units_sold,
        "storage_cost_per_unit_sold": per_unit_sold,
    }


def calculate_inbound_fees(
    region: str = "west",
    shipping_cost_per_shipment: float = 0.0,
    units_per_shipment: int = 1,
) -> Dict:
    region_key = (region or "west").lower()
    placement = INBOUND_BY_REGION.get(region_key, INBOUND_PLACEMENT_DEFAULT)
    shipping_per_unit = round(shipping_cost_per_shipment / max(units_per_shipment, 1), 2) if shipping_cost_per_shipment > 0 else 0.0
    total = round(placement + shipping_per_unit, 2)
    return {
        "inbound_region": region_key,
        "inbound_placement_fee_per_unit": placement,
        "shipping_cost_per_unit": shipping_per_unit,
        "total_inbound_cost_per_unit": total,
    }


def estimate_dimensions_from_weight(weight_lbs: float, category: str = "") -> ProductDimensions:
    """Estimate package size from weight/category when scrape has no dimensions."""
    cat = (category or "").lower()
    if any(k in cat for k in ("cell phone", "phone", "tablet")):
        # Typical retail phone box (~0.11 cu ft) aligns with Seller Central storage line
        return ProductDimensions(weight_lbs=weight_lbs, length_in=9.0, width_in=6.5, height_in=3.5)
    if weight_lbs <= 1:
        return ProductDimensions(weight_lbs=weight_lbs, length_in=10, width_in=8, height_in=2)
    if weight_lbs <= 3:
        return ProductDimensions(weight_lbs=weight_lbs, length_in=14, width_in=10, height_in=4)
    return ProductDimensions(weight_lbs=weight_lbs, length_in=18, width_in=12, height_in=6)