package lintgate

// Observes the exit status of `task lint` (the lint step of `task check`), not the lint
// rules themselves. It runs the repo's real Taskfile in a scratch module so a change to the
// lint command that stops it failing on findings (#41) turns this red.

import (
	"bytes"
	"errors"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strings"
	"testing"
)

const scratchWithFinding = `package main

import "os"

func main() { os.Remove("x") }
`

func scratchModule(t *testing.T) string {
	t.Helper()
	taskfile, err := os.ReadFile(filepath.Join("..", "..", "Taskfile.yml"))
	if err != nil {
		t.Fatalf("read Taskfile.yml: %v", err)
	}
	dir := t.TempDir()
	for name, body := range map[string]string{
		"Taskfile.yml": string(taskfile),
		"go.mod":       "module scratch\n\ngo 1.21\n",
		"main.go":      scratchWithFinding,
	} {
		if err := os.WriteFile(filepath.Join(dir, name), []byte(body), 0o644); err != nil {
			t.Fatalf("write %s: %v", name, err)
		}
	}
	return dir
}

// ansi matches the colour escape sequences task prints when it thinks it has a terminal.
var ansi = regexp.MustCompile("\x1b\\[[0-9;]*m")

// hasSkipNotice reports whether the skip notice was printed as output. Task echoes the command
// line first, and that line contains the same words, so a substring match would be vacuous.
func hasSkipNotice(out string) bool {
	for _, line := range strings.Split(ansi.ReplaceAllString(out, ""), "\n") {
		if strings.HasPrefix(line, "golangci-lint not installed") {
			return true
		}
	}
	return false
}

// runLint runs `task lint` in dir with the given PATH and returns its combined output and exit code.
func runLint(t *testing.T, dir, path string) (string, int) {
	t.Helper()
	return runTask(t, dir, path, "lint")
}

func runTask(t *testing.T, dir, path string, args ...string) (string, int) {
	t.Helper()
	taskBin, err := exec.LookPath("task")
	if err != nil {
		t.Skip("task not installed")
	}
	cmd := exec.Command(taskBin, args...)
	cmd.Dir = dir
	cmd.Env = append(os.Environ(), "PATH="+path)
	var out bytes.Buffer
	cmd.Stdout, cmd.Stderr = &out, &out
	err = cmd.Run()
	var exitErr *exec.ExitError
	switch {
	case err == nil:
		return out.String(), 0
	case errors.As(err, &exitErr):
		return out.String(), exitErr.ExitCode()
	default:
		t.Fatalf("run task lint: %v", err)
		return "", -1
	}
}

func TestTaskLint_ExitsNonZeroWhenGolangciLintReportsAFinding(t *testing.T) {
	if _, err := exec.LookPath("golangci-lint"); err != nil {
		t.Skip("golangci-lint not installed")
	}
	out, code := runLint(t, scratchModule(t), os.Getenv("PATH"))
	if code == 0 {
		t.Fatalf("task lint exited 0 on a module with an unchecked error; output:\n%s", out)
	}
	if hasSkipNotice(out) {
		t.Fatalf("task lint blamed a missing binary for a lint failure; output:\n%s", out)
	}
	if !strings.Contains(out, "errcheck") {
		t.Fatalf("a non-zero exit without the finding means the linter crashed, not that it found something; output:\n%s", out)
	}
}

// The lint step only gates anything if `task check` runs it.
func TestTaskCheck_RunsTheLintStep(t *testing.T) {
	out, code := runTask(t, scratchModule(t), os.Getenv("PATH"), "--dry", "check")
	if code != 0 {
		t.Fatalf("task --dry check exited %d; output:\n%s", code, out)
	}
	if !strings.Contains(out, "task: [lint]") {
		t.Fatalf("task check no longer runs the lint step; output:\n%s", out)
	}
}

func TestTaskLint_SkipsWithANoticeWhenGolangciLintIsAbsent(t *testing.T) {
	taskBin, err := exec.LookPath("task")
	if err != nil {
		t.Skip("task not installed")
	}
	bin := t.TempDir() // a PATH holding task and nothing else
	if err := os.Symlink(taskBin, filepath.Join(bin, "task")); err != nil {
		t.Fatalf("symlink task: %v", err)
	}
	out, code := runLint(t, scratchModule(t), bin)
	if code != 0 {
		t.Fatalf("task lint exited %d without golangci-lint on PATH; output:\n%s", code, out)
	}
	if !hasSkipNotice(out) {
		t.Fatalf("expected the skip notice; output:\n%s", out)
	}
}

// CI runs task with colour on, so the notice line starts with an escape sequence; a bare
// prefix match missed it there while passing on a terminal-less local run.
func TestHasSkipNotice_SeesTheNoticeBehindColourCodes(t *testing.T) {
	out := "\x1b[32mtask: [lint] ...\n\x1b[0mgolangci-lint not installed — skipping (CI installs it)\n"
	if !hasSkipNotice(out) {
		t.Fatalf("notice not found in coloured output: %q", out)
	}
	if hasSkipNotice("\x1b[32mtask: [lint] if command -v golangci-lint ...; echo \"golangci-lint not installed\"\n") {
		t.Fatal("the echoed command line must not count as the notice")
	}
}