ModelRouter/internal/lua/plugin_http_args.go

package lua

import (
	"fmt"
	"strings"
	"time"

	golua "github.com/aarzilli/golua/lua"
)

// httpArgIdx is the stack slot holding the caller's table. Verified against
// golua: a PushGoClosure function is invoked with its arguments already on top
// and nothing of itself below them.
const httpArgIdx = 1

// readHTTPRequestSpec decodes the Lua argument table:
//
//	__llmsproxy_http({
//	  url = "https://host/path",
//	  method = "GET",              -- optional, default GET
//	  headers = { ["X-A"] = "1" }, -- optional
//	  body = "...",                -- optional
//	  timeout_ms = 8000,           -- optional, clamped to 60s
//	})
//
// The table is at index 1: measured, not assumed. A Go closure registered with
// PushGoClosure is NOT on the stack when it runs — GetTop() is 1 and slot 1 is
// the caller's table (type LUA_TTABLE). An earlier version assumed the closure
// occupied slot 1 and read from slot 2, which then reported "expected a table
// argument" for a perfectly good call.
//
// luaTableToGoValue already turns the table into a map/slice, so the whole
// argument is decoded in one pass instead of walking the table field by field.
func readHTTPRequestSpec(L *golua.State) (httpRequestSpec, error) {
	var spec httpRequestSpec
	if L.GetTop() < httpArgIdx {
		return spec, fmt.Errorf("__llmsproxy_http: expected a table argument")
	}
	if L.Type(httpArgIdx) != golua.LUA_TTABLE {
		return spec, fmt.Errorf("__llmsproxy_http: expected a table, got %s",
			normalizeString(L, httpArgIdx))
	}
	arg, ok := luaTableToGoValue(L, httpArgIdx).(map[string]interface{})
	if !ok {
		return spec, fmt.Errorf("__llmsproxy_http: argument must be a keyed table")
	}
	for k, v := range arg {
		switch strings.ToLower(k) {
		case "url", "uri", "endpoint":
			spec.URL = asString(v)
		case "method", "verb":
			spec.Method = asString(v)
		case "body", "data", "payload":
			spec.Body = asString(v)
		case "headers", "header":
			if m, ok := v.(map[string]interface{}); ok {
				spec.Headers = make(map[string]string, len(m))
				for hk, hv := range m {
					spec.Headers[hk] = asString(hv)
				}
			}
		case "timeout_ms", "timeoutms":
			if n, ok := asFloat(v); ok {
				spec.Timeout = time.Duration(n) * time.Millisecond
			}
		}
	}
	if spec.URL == "" {
		return spec, fmt.Errorf("__llmsproxy_http: missing url")
	}
	return spec, nil
}

// pushHTTPResponse converts the result into two Lua values: a table
// {status, headers, body} and nil. The caller pushes the error slot itself.
func pushHTTPResponse(L *golua.State, r *httpResult) {
	L.NewTable()

	L.PushString("status")
	L.PushNumber(float64(r.Status))
	L.SetTable(-3)

	L.PushString("headers")
	pushStringMap(L, r.Headers)
	L.SetTable(-3)

	L.PushString("body")
	L.PushString(r.Body)
	L.SetTable(-3)
}

func pushStringMap(L *golua.State, m map[string]string) {
	L.NewTable()
	for k, v := range m {
		L.PushString(v)
		L.SetField(-2, k)
	}
}

func asString(v interface{}) string {
	switch t := v.(type) {
	case string:
		return t
	case nil:
		return ""
	default:
		return fmt.Sprintf("%v", t)
	}
}

func asFloat(v interface{}) (float64, bool) {
	switch t := v.(type) {
	case float64:
		return t, true
	case int:
		return float64(t), true
	case int64:
		return float64(t), true
	default:
		return 0, false
	}
}