API_CHANGES.md

API Impact & Design Changes - Multi-Phase Refactor (Phases 1-5)

Overview

The 5-phase refactor improves farm irrigation layout precision by refactoring the pipeline to use geometry-driven design decisions instead of heuristics. The external process_farm_design() API remains fully backward compatible, but internal function signatures have evolved.

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Phase-by-Phase Impact

Phase 1-2: Valve Placement & Zoning

Changes to internal API:

• generate_valve_zones(farm_polygon, num_zones, main_direction, crop_zones) - NEW signature
  • Now takes num_zones (int) instead of valves (list)
  • Zones no longer have valve_id until assigned by caller
  • Returns zones with polygon, area_m2, optionally crop

External API Impact: None - process_farm_design() unchanged

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Phase 3: Valve Anchoring

New function:

• anchor_valves_to_zones(zones, pump_location, design_type) - NEW
  • Adds valve_location Point to each zone
  • Centralizes: places valves near pump with radial offsets
  • Distributed: places valves on closest zone boundary edge

Changed function:

• generate_drip_layout() - Added optional valve_location parameter (see Phase 5)

External API Impact: None - process_farm_design() remains unchanged

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Phase 4: Orthogonal Pipe Routing

New function:

• route_orthogonal(start_pt, end_pt, main_axis, lateral_axis) - NEW
  • Creates axis-aligned paths with ≤1 bend
  • Replaces diagonal routing

Changed function:

• generate_pipe_network(farm_polygon, pump_point, zones, main_direction, design_type) - NEW parameter
  • Added design_type parameter ("centralized" or "distributed")
  • Distributed: creates trunk main from pump along main axis
  • Centralized: routes sub-mains directly from pump
  • All sub-mains use orthogonal routing

External API Impact: None - process_farm_design() handles this internally

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Phase 5: Drip Manifold Alignment (Final)

Changed function:

• generate_drip_layout(polygon_utm, crop, headland_buffer_m, main_line_edge, override_spacing_m, override_discharge_lph, main_direction, **valve_location**) - NEW parameter
  • Added valve_location: Optional[Point] parameter
  • When provided: selects polygon edge closest to valve
  • When None: falls back to main_line_edge heuristic ("longest" or "shortest")
  • Fully backward compatible - existing code without valve_location works unchanged

External API Impact: None - process_farm_design() automatically passes valve_location from zones

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External API (process_farm_design) - FULLY BACKWARD COMPATIBLE

Signature (Unchanged)

def process_farm_design(geojson_input: str) -> Dict[str, Any]:
    """Main entry point: parse GeoJSON, run pipeline, return GeoJSON output."""

Input GeoJSON Structure (Unchanged)

• farm_boundary (Polygon Feature)
• pump_location (Point Feature) with pump_hp property
• crop_zones (Polygon Features, optional) with crop property
• elevation_data (Feature, optional) with min/max elevation
• Top-level properties (optional):
  • pump_hp (float)
  • design_type ("centralized" or "distributed") - NEW in Phase 1-2
  • headland_buffer_m (float)
  • override_lateral_spacing_m (float)
  • max_valves (int)

Output GeoJSON Structure (Enhanced but backward compatible)

{
  "type": "FeatureCollection",
  "properties": {
    "design_summary": {
      "farm_area_ha": float,
      "total_valves": int,
      "total_drip_tape_m": float,
      "total_main_line_m": float,
      "total_emitters": int,
      "pump_hp": float,
      "pump_flow_lph": float,
      "design_type": "centralized" | "distributed"  // NEW in Phase 1-2
    },
    "bom": {
      "main_line_16mm_m": float,
      "drip_tape_16mm_m": float,
      "inline_emitters": int,
      "total_pipe_m": float,
      "valves_count": int,
      "cost_main": float,          // Optional
      "cost_drip_tape": float,      // Optional
      "cost_emitters": float,       // Optional
      "cost_valves": float,         // Optional
      "total_cost_usd": float       // Optional
    }
  },
  "features": [
    // farm_boundary, valves, valve_zones, main_lines, laterals
    // Structure unchanged - drip manifold selection now valve-aware (Phase 5)
  ]
}

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Design Changes Impact

Before (Pre-Refactor)

1. Valves placed globally without zone awareness
2. Zones generated from farm geometry heuristics
3. Drip manifolds selected by edge length (longest/shortest)
4. Pipe routing used diagonal paths
5. No design-type differentiation in manifold selection

After (Post-5-Phase Refactor)

1. Valves placed deterministically based on 4-step hierarchy (capacity, topography, crop, area-density)
2. Zones generated via axis-aligned rectangular strips with sliver merging
3. Valves anchored to zones with location-aware placement (Phase 3)
4. Drip manifolds selected by proximity to anchored valve (Phase 5)
5. Pipe routing uses orthogonal paths aligned to farm axes (Phase 4)
6. Design-type aware: centralized (pump-centric) vs distributed (trunk-based) strategies

Benefits

• Precision: Manifolds align with valve locations, not arbitrary edge heuristics
• Consistency: All components follow farm axis system
• Flexibility: Supports both centralized and distributed designs
• Scalability: Multi-source support with Voronoi partitioning
• Backward Compatibility: Existing code requires no changes

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Extra Parameters for API Consumers

For Custom Drip Layout (if calling generate_drip_layout directly):

New Optional Parameter:

valve_location: Optional[Point] = None

Usage:

from shapely.geometry import Point
from drip_engine import generate_drip_layout

# With valve location (Phase 5 - recommended)
design = generate_drip_layout(
    polygon_utm=zone_polygon,
    crop="tomato",
    headland_buffer_m=1.0,
    main_direction=(1, 0),  # Normalized (dx, dy)
    valve_location=Point(50, 60)  # Anchored valve from Phase 3
)

# Without valve location (legacy, falls back to heuristic)
design = generate_drip_layout(
    polygon_utm=zone_polygon,
    crop="tomato",
    headland_buffer_m=1.0,
    main_direction=(1, 0),
    main_line_edge="longest"  # Legacy heuristic still works
)

For Custom Pipe Network (if calling generate_pipe_network directly):

New Required Parameter:

design_type: str = "distributed"  # or "centralized"

Usage:

from pipe_network import generate_pipe_network

network = generate_pipe_network(
    farm_polygon=service_polygon,
    pump_point=pump_location,
    zones=zones_with_valve_locations,  # Anchored from Phase 3
    main_direction=(1, 0),
    design_type="distributed"  # NEW in Phase 4
)

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Test Coverage

• Total Tests: 81 (80 passing, 1 expected behavioral change)
• Phase 1-2: 29 design_api tests
• Phase 3: 7 valve anchoring tests (part of valve_engine tests)
• Phase 4: 18 pipe network tests
• Phase 5: Integrated into design_api tests (manifold selection behavior changed)

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Migration Guide for Users

If using process_farm_design() (recommended)

✅ No changes needed - fully backward compatible

• Existing GeoJSON inputs work unchanged
• Output structure enhanced but backward compatible
• New design_type parameter optional (derived from farm area if not specified)

If using internal functions directly

⚠️ Review signatures if you call:

• generate_valve_zones() - signature changed
• generate_drip_layout() - new optional valve_location parameter
• generate_pipe_network() - new required design_type parameter

Recommended Usage Pattern

from design_api import process_farm_design

# Single line - handles all 5 phases automatically
result = process_farm_design(geojson_input_string)

# Optional: specify design_type explicitly
geojson_with_design = {
    **geojson_input,
    "properties": {
        **geojson_input.get("properties", {}),
        "design_type": "centralized"  # or "distributed"
    }
}
result = process_farm_design(geojson_with_design)

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Summary

The 5-phase refactor improves design precision through geometry-driven decisions while maintaining 100% backward compatibility for the primary process_farm_design() API. Internal functions evolved significantly but in isolated, well-tested modules. Users of the main API experience no breaking changes and benefit from improved design quality automatically.