package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"os/exec"
	"path"
	"regexp"
	"strings"
	"github.com/kylelemons/godebug/diff"
)

func fileExists(f string) bool {
	_, err := os.Stat(f);
	return err == nil;
}

var inputre = regexp.MustCompile(`\.input$`)

type CPTest struct {
	Name string
	Input *[]byte
	Output *[]byte
}

func runOneTest(dir string, test *CPTest) {
	fmt.Println("Running Test", test.Name, "...");
	fmt.Println("==========");
	fmt.Println("INPUT:")
	fmt.Println(string(*test.Input));

	fmt.Println("==========");
	cmd := exec.Command("go", "run", path.Join(dir, "main.go"));
	inpipe, _ := cmd.StdinPipe();
	defer inpipe.Close();

	fmt.Fprintln(inpipe, string(*test.Input));
	out,err := cmd.Output(); 
	if err != nil {
		fmt.Println(err);
		return
	}
	fmt.Println("OUTPUT:")
	fmt.Println(string(out));

	if test.Output != nil {
		fmt.Println("==========");
		fmt.Println("ANSWER:")
		fmt.Println(string(*test.Output));
		fmt.Println("==========");
		fmt.Println("DIFF:")
		fmt.Println(diff.Diff(string(out), string(*test.Output)))
	}
	fmt.Println("==========");
}

func runTests(dir string, selected []string) {
	testfolder := path.Join(dir, "cpgo_tests")
	info, err := os.Stat(testfolder);
	if err != nil {
		fmt.Println("Error encountered", err);
		os.Exit(1);
	}
	if !info.IsDir() {
		fmt.Println(testfolder, "is not a directory.")
		os.Exit(1);
	}
	entries, err := ioutil.ReadDir(testfolder); if err != nil {
		fmt.Println("Error while accessing", testfolder, err);
		os.Exit(1);
	}
	tests := make([]CPTest, 0);
	testmap := map[string]*CPTest{};
	for _,file := range entries {
		if strings.HasSuffix(file.Name(), ".input") {
			fpath := path.Join(testfolder, file.Name());
			input,_ := ioutil.ReadFile(fpath);
			outputfile := string(inputre.ReplaceAll([]byte(fpath), []byte(".output")));
			tst := CPTest{
				Name: strings.TrimSuffix(file.Name(), ".input"),
				Input: &input,
			};
			if fileExists(outputfile) {
				out,_ := ioutil.ReadFile(outputfile);
				tst.Output = &out;
			}
			tests = append(tests, tst);
			testmap[tst.Name] = &tst;
		}
	}
	if len(selected) == 0 {
		for _, t := range tests {
			runOneTest(dir, &t);
		}
	} else {
		for _,name := range selected {
			t, exists := testmap[name];
			if exists {
				runOneTest(dir, t);
			} else {
				fmt.Println(name, "is not a valid test.");
				return
			}
		}
	}
}