Conditional Field Extraction

# Conditional Field Extraction
#
# Uses the condition system to apply json_body_field only on
# specific request paths. Requests to /v1/ get the "model"
# field extracted into X-Model; all other paths skip body
# inspection entirely, avoiding unnecessary buffering.
#
# This is useful when a single gateway serves both AI
# inference endpoints (which need body-based routing) and
# static or administrative endpoints (which do not).
#
# Usage:
#   cargo run -p praxis-proxy -- -c examples/configs/payload-processing/conditional-field-extraction.yaml
#
#   # Body inspected, X-Model extracted:
#   curl -X POST http://localhost:8080/v1/chat/completions \
#     -H "Content-Type: application/json" \
#     -d '{"model": "model-beta-1", "messages": [...]}'
#
#   # Body NOT inspected, forwarded directly:
#   curl http://localhost:8080/healthz

listeners:
  - name: gateway
    address: "0.0.0.0:8080" # dev value; binds all interfaces
    filter_chains:
      - conditional-extraction
      - routing

filter_chains:
  - name: conditional-extraction
    filters:
      - filter: json_body_field
        conditions:
          - when:
              path_prefix: "/v1/"
        field: model
        header: X-Model

  - name: routing
    filters:
      - filter: router
        routes:
          - path_prefix: "/v1/"
            headers:
              x-model: "model-beta-1"
            cluster: beta_cluster
          - path_prefix: "/v1/"
            cluster: default-inference
          - path_prefix: "/"
            cluster: static
      - filter: load_balancer
        clusters:
          - name: beta_cluster
            endpoints:
              - "10.0.1.1:8080"
          - name: default-inference
            endpoints:
              - "10.0.2.1:8080"
          - name: static
            endpoints:
              - "10.0.3.1:8080"