package main

import (
	"bytes"
	"fmt"
	"go/ast"
	"go/parser"
	"go/printer"
	"go/token"
	"runtime"
)

func main() {
	assert(1 < 2)
	assert(1 > 2)
}

func assert(cond bool) {
	if cond {
		return
	}

	pc, file, line, ok := runtime.Caller(0)
	fmt.Println(pc, file, line, ok)

	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, file, nil, parser.ParseComments)
	if err != nil {
		panic(err)
	}

	ast.Inspect(f, func(node ast.Node) bool {
		if callExpr, ok := node.(*ast.CallExpr); ok {
			ident, ok := callExpr.Fun.(*ast.Ident)
			if !ok {
				return true
			}

			if ident.Name == "assert" { // TODO: use runtime.FuncForPC
				var buf bytes.Buffer
				printer.Fprint(&buf, fset, callExpr.Args[0])
				fmt.Println("args", buf.String())
			}
		}
		return true
	})
}

// Output:
// 5112365 /tmp/main.go 25 true
// args 1 < 2
// args 1 > 2