Build an Open Network Logistics Accessibility and Drop-Off Coordinator — implementation

## Build
Coordinate mock last-mile courier assignments across decentralized delivery networks using Beckn protocol schemas. Match specialized recipient accessibility requirements with courier physical mobility parameters.

## User
Delivery hub operations coordinator managing accessible parcel dispatch for elderly and mobility-impaired recipients.

## Workflow
1. Parse incoming Beckn fulfillment requests containing recipient accessibility constraints and landmark directions.
2. Cross-reference courier equipment capabilities and delivery vehicle access constraints against recipient physical barriers.
3. Synthesize a validated Beckn on_confirm fulfillment packet containing step-by-step accessible drop-off instructions.
4. Simulate asynchronous callback telemetry and generate exception manifests when courier parameters do not meet accessibility needs.

## Interface
Dispatcher workspace showing pending fulfillment orders, courier constraint filters, and generated Beckn protocol callback logs.

## Data
Generate 30 synthetic Beckn fulfillment payloads containing varying accessibility profiles (staircase-only, elevator outage, landmark drop-off) stored in local JSON format.
Starter examples below are synthetic. They are not downloaded records.

## Source
[Beckn protocol specifications](https://raw.githubusercontent.com/beckn/protocol-specifications/master/README.md)
Uses Beckn protocol core transaction packet structure with context and message separation and asynchronous server-to-server callback conventions.

## Tools
langgraph, fastapi, pydantic.
LangGraph manages stateful multi-step routing logic between incoming Beckn order intents, constraint matching, and callback generation.
Local or hosted LLM with multi-step reasoning capabilities and JSON mode output.

## Deliverables
Submit runnable source, pinned dependencies, setup commands, a working interface, example outputs, and a recorded end-to-end demo. Include tests and an action log.

## Acceptance
- Validates incoming Beckn context headers including domain, action, and transaction_id.
- Correctly matches courier vehicle and physical capacity against building barrier profiles.
- Outputs compliant Beckn on_confirm message payloads with complete fulfillment metadata.
- Generates a structured exception notice when accessibility criteria cannot be fulfilled.

## Starter Examples
```json
[
  {
    "input": {
      "context": {
        "domain": "nic2004:55204",
        "action": "confirm",
        "transaction_id": "tx_logistics_101",
        "bap_id": "mock_buyer_app.org",
        "bpp_id": "mock_logistics_pp.org"
      },
      "message": {
        "order": {
          "id": "ord_9901",
          "fulfillment": {
            "end": {
              "location": {
                "address": "Flat 302, Green Heights, Pune",
                "accessibility_flags": [
                  "elevator_available",
                  "wheelchair_ramp"
                ]
              }
            }
          }
        },
        "courier_profile": {
          "courier_id": "c_44",
          "transport_mode": "two_wheeler",
          "max_carry_weight_kg": 15
        }
      }
    },
    "expected_output": {
      "context": {
        "domain": "nic2004:55204",
        "action": "on_confirm",
        "transaction_id": "tx_logistics_101"
      },
      "message": {
        "order": {
          "id": "ord_9901",
          "status": "ACCEPTED",
          "fulfillment": {
            "state": "ASSIGNED",
            "assigned_courier_id": "c_44",
            "dropoff_instructions": "Use ground ramp and take elevator directly to floor 3."
          }
        }
      },
      "accessibility_matched": true
    }
  },
  {
    "input": {
      "context": {
        "domain": "nic2004:55204",
        "action": "confirm",
        "transaction_id": "tx_logistics_102",
        "bap_id": "mock_buyer_app.org",
        "bpp_id": "mock_logistics_pp.org"
      },
      "message": {
        "order": {
          "id": "ord_9902",
          "fulfillment": {
            "end": {
              "location": {
                "address": "Floor 4, Old Chawl, Girgaon, Mumbai",
                "accessibility_flags": [
                  "staircase_only",
                  "narrow_corridor",
                  "weight_heavy_25kg"
                ]
              }
            }
          }
        },
        "courier_profile": {
          "courier_id": "c_12",
          "transport_mode": "bicycle",
          "max_carry_weight_kg": 10
        }
      }
    },
    "expected_output": {
      "context": {
        "domain": "nic2004:55204",
        "action": "on_confirm",
        "transaction_id": "tx_logistics_102"
      },
      "message": {
        "order": {
          "id": "ord_9902",
          "status": "REJECTED",
          "fulfillment": {
            "state": "UNASSIGNED",
            "assigned_courier_id": null,
            "dropoff_instructions": null
          }
        }
      },
      "accessibility_matched": false,
      "rejection_reason": "courier_weight_and_staircase_limit_exceeded"
    }
  }
]
```

## Safety
All carrier allocations and status callbacks are executed in a simulated sandbox environment without actual financial or delivery liabilities.
Use mock external writes. Require human review before any real deployment.