code/docs/RoughPlan.md

2. The Action Space (Discrete: Size 11)

Expanded to accommodate the three crop types.

• 0: Wait: Do nothing.
• 1: Plant_Crop_1 (Heavy): High seed cost, high profit, destroys soil nitrogen.
• 2: Plant_Crop_2 (Medium): Moderate seed cost, moderate profit, mild nitrogen drain.
• 3: Plant_Crop_3 (Legume): Low seed cost, lower profit, restores soil nitrogen.
• 4: Irrigate: Spends Cost_Irrigate, mitigates drought penalty.
• 5: Fertilize: Spends Cost_Fertilize, boosts Soil_Nitrogen.
• 6: Harvest_and_Store: Calculates yield. Auto-sells existing inventory, overwrites with new yield, resets land.
• 7: Harvest_and_Sell: Calculates yield, immediately converts to cash at spot price, resets land.
• 8: Sell_Inventory: Empties the storage slot for cash at current market price.
• 9: Take_Loan: Injects fixed cash chunk, adds to Current_Debt.
• 10: Repay_Loan: Uses cash to pay down Current_Debt.
• [Future Scope] 11: Repair_Machinery.

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3. Environment Dynamics (The Physics & Economics Engine)

This is the core logic calculated inside the step() function.

A. Weather Generation Engine

Rainfall isn't purely random; it is seasonal with stochastic noise.

• The Math: Let $m$ be the current month. The expected rainfall $W_t$ is calculated using a seasonal baseline $\mu(m)$ plus Gaussian noise $\epsilon \sim \mathcal{N}(0, \sigma^2)$. $$W_t = \max(0, \min(1, \mu(m) + \epsilon))$$
• Logic:
  • If $m \in {6, 7, 8, 9}$ (Monsoon): $\mu(m) = 0.8$ (Heavy rain likely).
  • If $m \in {10, 11, 12, 1}$ (Winter): $\mu(m) = 0.2$ (Dry, but stable).
  • If $m \in {4, 5}$ (Summer): $\mu(m) = 0.05$ (Extreme dry heat).

B. Dynamic Interest Rate Calculation

The bank reacts to both the calendar (farmer demand) and the sky (default risk).

• The Math: The current interest rate $R_{interest}$ is updated every month: $$R_{interest} = R_{base} + \Delta_{liquidity}(m) + \Delta_{risk}(W_{deficit})$$
• Logic:
  • $R_{base}$: Standard bank rate (e.g., $0.08$ or $8%$).
  • $\Delta_{liquidity}$: If $m \in {6, 7}$ (Planting season), add $0.03$ because everyone wants cash. If $m \in {10, 11}$ (Harvest), subtract $0.02$.
  • $\Delta_{risk}$: If the generated $W_t$ is significantly lower than the Optimal_Rainfall for the active crop, lenders panic. $W_{deficit} = \text{Optimal} - W_t$. If $W_{deficit} > 0.3$, add $0.05$ to the interest rate to price in the drought risk.

C. The Spoilage & Overwrite Rules

• Every month, Stored_Age_Months increases by 1. If it exceeds 6, the crop rots (Stored_Amount = 0).
• If Harvest_and_Store is chosen while the silo is full, the old crop is automatically liquidated at this month's market price, and the newly harvested crop takes its place.

D. Trajectory Horizon (Configurable)

• Hackathon MVP: Episode terminates at $T = 60$ steps (5 years).
• Future Scope: Increase to $T = 120$ or $T = 240$ (10–20 years). Longer trajectories strictly force the agent to learn the value of the Legume crop, as synthetic fertilizer costs will eventually outpace profits if soil is continually abused over a decade.

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4. The Reward Function

The reward calculates the financial delta, heavily penalizes impossible actions, and provides a terminal payout.

• Monthly Cash Flow: $$R_t = \text{Cash}t - \text{Cash}{t-1}$$
• Rule Enforcement Penalties: $-50$ for invalid actions (e.g., planting on occupied land, harvesting empty land).
• Bankruptcy Termination: $-1000$ and done = True if $\text{Cash} < 0$ and borrowing limit is reached.
• Terminal Liquidation (Step 60 ONLY): $$R_{final} = (\text{Soil_Nitrogen} \times 10,000) + (\text{Active_Crop_Value}) + (\text{Stored_Crop_Value})$$
• [Future Scope Penalties]:
  • Subtract a fixed $C_{storage} \times \text{Stored_Amount}$ every step.
  • Subtract $C_{depreciation}$ every time a physical action (Plant, Harvest, Irrigate) is taken, requiring the agent to eventually spend cash to repair.

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