greq/internal/api/lua_test_runner.go

package api

import (
	"encoding/json"
	"fmt"
	"strings"

	lua "github.com/yuin/gopher-lua"
)

// TestResult holds the outcome of a single test assertion.
type TestResult struct {
	Pass    bool
	Message string
}

// RunLuaTestScript executes a Lua script against a Response.
//
// Globals available in the script:
//
//	status       (number)  HTTP status code, e.g. 200
//	status_text  (string)  Full status string, e.g. "200 OK"
//	body         (string)  Raw response body
//	headers      (table)   Response headers, lower-cased keys
//	json_body    (table)   Parsed JSON body, or nil if not JSON
//	duration_ms  (number)  Round-trip duration in milliseconds
//	size         (number)  Response body size in bytes
//
// Helper functions:
//
//	pass(message)          Record a passing assertion
//	fail(message)          Record a failing assertion (does NOT abort the script)
//	assert_eq(a, b, msg)   fail(msg) if a ~= b, else pass(msg)
//	assert_status(code)    assert_eq(status, code, "status == "..code)
//	json_decode(str)       Parse a JSON string → Lua table
func RunLuaTestScript(script string, resp *Response) ([]TestResult, error) {
	if strings.TrimSpace(script) == "" {
		return nil, nil
	}

	L := lua.NewState(lua.Options{SkipOpenLibs: false})
	defer L.Close()

	var results []TestResult

	// Inject pass / fail helpers
	L.SetGlobal("pass", L.NewFunction(func(L *lua.LState) int {
		msg := L.OptString(1, "")
		results = append(results, TestResult{Pass: true, Message: msg})
		return 0
	}))
	L.SetGlobal("fail", L.NewFunction(func(L *lua.LState) int {
		msg := L.OptString(1, "")
		results = append(results, TestResult{Pass: false, Message: msg})
		return 0
	}))
	L.SetGlobal("assert_eq", L.NewFunction(func(L *lua.LState) int {
		a := L.Get(1)
		b := L.Get(2)
		msg := L.OptString(3, fmt.Sprintf("%v == %v", a, b))
		if lua.LVCanConvToString(a) && lua.LVCanConvToString(b) &&
			lua.LVAsString(a) == lua.LVAsString(b) {
			results = append(results, TestResult{Pass: true, Message: msg})
		} else {
			results = append(results, TestResult{
				Pass:    false,
				Message: fmt.Sprintf("%s (got %v, expected %v)", msg, a, b),
			})
		}
		return 0
	}))
	L.SetGlobal("assert_status", L.NewFunction(func(L *lua.LState) int {
		expected := L.CheckInt(1)
		msg := fmt.Sprintf("status == %d", expected)
		if resp.StatusCode == expected {
			results = append(results, TestResult{Pass: true, Message: msg})
		} else {
			results = append(results, TestResult{
				Pass:    false,
				Message: fmt.Sprintf("%s (got %d)", msg, resp.StatusCode),
			})
		}
		return 0
	}))

	// json_decode helper
	L.SetGlobal("json_decode", L.NewFunction(func(L *lua.LState) int {
		s := L.CheckString(1)
		var v interface{}
		if err := json.Unmarshal([]byte(s), &v); err != nil {
			L.Push(lua.LNil)
			L.Push(lua.LString(err.Error()))
			return 2
		}
		L.Push(goToLua(L, v))
		return 1
	}))

	// Set response globals
	L.SetGlobal("status", lua.LNumber(resp.StatusCode))
	L.SetGlobal("status_text", lua.LString(resp.Status))
	L.SetGlobal("body", lua.LString(resp.Body))
	L.SetGlobal("duration_ms", lua.LNumber(resp.Duration.Milliseconds()))
	L.SetGlobal("size", lua.LNumber(resp.Size))

	// headers table (lower-cased keys)
	headersTbl := L.NewTable()
	for k, vals := range resp.Headers {
		if len(vals) > 0 {
			L.SetField(headersTbl, strings.ToLower(k), lua.LString(vals[0]))
		}
	}
	L.SetGlobal("headers", headersTbl)

	// json_body: parse resp.Body if JSON
	var jsonBody interface{}
	if resp.IsJSON {
		if err := json.Unmarshal([]byte(resp.Body), &jsonBody); err == nil {
			L.SetGlobal("json_body", goToLua(L, jsonBody))
		} else {
			L.SetGlobal("json_body", lua.LNil)
		}
	} else {
		L.SetGlobal("json_body", lua.LNil)
	}

	if err := L.DoString(script); err != nil {
		// Include any results collected before the error
		errResult := TestResult{
			Pass:    false,
			Message: "Lua error: " + err.Error(),
		}
		results = append(results, errResult)
		return results, nil // return results, not the error, so UI can display them
	}

	return results, nil
}

// goToLua converts a Go value (from json.Unmarshal) into a lua.LValue.
func goToLua(L *lua.LState, v interface{}) lua.LValue {
	if v == nil {
		return lua.LNil
	}
	switch val := v.(type) {
	case bool:
		return lua.LBool(val)
	case float64:
		return lua.LNumber(val)
	case string:
		return lua.LString(val)
	case []interface{}:
		tbl := L.NewTable()
		for i, item := range val {
			tbl.RawSetInt(i+1, goToLua(L, item))
		}
		return tbl
	case map[string]interface{}:
		tbl := L.NewTable()
		for k, item := range val {
			L.SetField(tbl, k, goToLua(L, item))
		}
		return tbl
	default:
		return lua.LString(fmt.Sprintf("%v", val))
	}
}