package builder

import (
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

// novox/hq issue 310: the build seat ran the merge-check.sh found in the pull request's head, so a change
// could delete or gut it and skip its own tests, and a branch cut before the script escaped them. The base
// branch's script — its parts and its toolchain with it — judges the change's tree.

// aPullRequest is a repository whose main holds base, and a branch "change" off it that holds change on
// top (a nil body deletes the file): cloned as the check clones it, at the change's head. It answers the
// clone's tree.
func aPullRequest(t *testing.T, base, change map[string]*string) string {
	t.Helper()
	origin := t.TempDir()
	git := func(dir string, args ...string) string {
		t.Helper()
		cmd := exec.Command("git", args...)
		cmd.Dir = dir
		cmd.Env = append(os.Environ(), "GIT_AUTHOR_NAME=t", "GIT_AUTHOR_EMAIL=t@example.org",
			"GIT_COMMITTER_NAME=t", "GIT_COMMITTER_EMAIL=t@example.org")
		out, err := cmd.CombinedOutput()
		if err != nil {
			t.Fatalf("git %v: %v\n%s", args, err, out)
		}
		return strings.TrimSpace(string(out))
	}
	write := func(files map[string]*string) {
		for name, body := range files {
			at := filepath.Join(origin, name)
			if body == nil {
				if err := os.Remove(at); err != nil {
					t.Fatal(err)
				}
				continue
			}
			if err := os.MkdirAll(filepath.Dir(at), 0o755); err != nil {
				t.Fatal(err)
			}
			if err := os.WriteFile(at, []byte(*body), 0o755); err != nil {
				t.Fatal(err)
			}
		}
		git(origin, "add", "-A")
		git(origin, "commit", "--quiet", "--allow-empty", "-m", "x")
	}
	git(origin, "init", "--quiet", "-b", "main")
	write(base)
	git(origin, "checkout", "--quiet", "-b", "change")
	write(change)
	head := git(origin, "rev-parse", "HEAD")
	git(origin, "checkout", "--quiet", "main")

	root := t.TempDir()
	git(root, "clone", "--quiet", origin, "checked")
	tree := filepath.Join(root, "checked")
	git(tree, "checkout", "--quiet", head)
	return tree
}

func s(body string) *string { return &body }

// judged runs the check that judges the change as the build seat would — each part a plain sh here.
func judged(t *testing.T, tree, base string) (Judging, *Layer) {
	t.Helper()
	j, err := TheCheckThatJudges(t.Context(), tree, base)
	if err != nil {
		t.Fatal(err)
	}
	if j.Script == nil {
		return j, nil
	}
	if err := j.Put(tree); err != nil {
		t.Fatal(err)
	}
	var out tail
	layer := ownCheck(t.Context(), CheckSpec{Toolchain: "go-image", Toolchains: map[string]string{"go": "go-image",
		"typescript": "ts-image"}}, ScriptParts(j.Script), tree, &out, func() bool { return false },
		func(image, script string) *exec.Cmd {
			cmd := exec.CommandContext(t.Context(), "sh", script)
			cmd.Dir = tree
			return cmd
		}, func(string, string, ...any) {})
	return j, layer
}

// main's check: the suite fails unless the tree holds what main requires.
const mainsCheck = "#!/bin/sh\nset -eu\ntest -f covered || { echo 'FAIL: the suite does not pass'; exit 1; }\n"

func TestAHeadWithoutTheScriptIsJudgedByMains(t *testing.T) {
	// Deleted by the change — or never there, on a branch cut before main had it: the head lacks it.
	tree := aPullRequest(t, map[string]*string{CheckScript: s(mainsCheck)}, map[string]*string{CheckScript: nil})
	j, layer := judged(t, tree, "main")
	if layer == nil || layer.Verdict != "fail" || !strings.Contains(layer.Summary, "does not pass") {
		t.Fatalf("a head without the script answered %+v — main's script was not what judged it", layer)
	}
	if !strings.Contains(j.Said, "the change holds no "+CheckScript) || !strings.Contains(j.Said, "main's judged it") {
		t.Errorf("the verdict does not say main's judged it: %q", j.Said)
	}

	// And a head that holds what main's script asks passes by it.
	tree = aPullRequest(t, map[string]*string{CheckScript: s(mainsCheck)},
		map[string]*string{CheckScript: nil, "covered": s("x")})
	if _, layer = judged(t, tree, "main"); layer == nil || layer.Verdict != "pass" {
		t.Fatalf("a head main's script passes answered %+v", layer)
	}
}

func TestAHeadThatGutsTheScriptIsStillJudgedByMains(t *testing.T) {
	tree := aPullRequest(t, map[string]*string{CheckScript: s(mainsCheck)},
		map[string]*string{CheckScript: s("#!/bin/sh\nexit 0\n")})
	j, layer := judged(t, tree, "main")
	if layer == nil || layer.Verdict != "fail" {
		t.Fatalf("a gutted script answered %+v — the change's own copy judged it", layer)
	}
	if !strings.Contains(j.Said, "ALTERS ITS OWN CHECK") || !strings.Contains(j.Said, CheckScript) {
		t.Errorf("the verdict does not say the change alters its check: %q", j.Said)
	}

	// Gutting the declared part instead, or declaring none: main's lines and main's part still judge.
	two := "#!/bin/sh\n# mesh-check-toolchain: typescript\n# mesh-check-also: go replays/merge-check.sh\nexit 0\n"
	tree = aPullRequest(t, map[string]*string{CheckScript: s(two), "replays/merge-check.sh": s(mainsCheck)},
		map[string]*string{CheckScript: s("#!/bin/sh\n# mesh-check-toolchain: typescript\nexit 0\n"),
			"replays/merge-check.sh": s("exit 0\n")})
	j, layer = judged(t, tree, "main")
	if layer == nil || layer.Verdict != "fail" || !strings.Contains(layer.Summary, "replays/merge-check.sh failed") {
		t.Fatalf("a gutted part answered %+v", layer)
	}
	if parts := ScriptParts(j.Script); len(parts) != 2 || parts[0].Toolchain != "typescript" {
		t.Errorf("main's toolchain and parts did not judge: %+v", parts)
	}
	if !strings.Contains(j.Said, CheckScript+", replays/merge-check.sh") {
		t.Errorf("the verdict does not name both altered scripts: %q", j.Said)
	}
}

// A change that legitimately alters the check is judged by main's, says so, and passes when main's passes:
// its own version judges the pull requests after it.
func TestAChangeToTheCheckIsJudgedByTheOneItReplaces(t *testing.T) {
	tree := aPullRequest(t, map[string]*string{CheckScript: s(mainsCheck), "covered": s("x")},
		map[string]*string{CheckScript: s(mainsCheck + "test -f also-covered\n")})
	j, layer := judged(t, tree, "main")
	if layer == nil || layer.Verdict != "pass" || !strings.Contains(j.Said, "ALTERS ITS OWN CHECK") {
		t.Fatalf("a change to the check answered %+v, said %q", layer, j.Said)
	}
	// The same script as main's: nothing to say.
	tree = aPullRequest(t, map[string]*string{CheckScript: s(mainsCheck), "covered": s("x")},
		map[string]*string{"other.go": s("package x\n")})
	if j, layer = judged(t, tree, "main"); layer == nil || layer.Verdict != "pass" || j.Said != "" {
		t.Fatalf("an unchanged check answered %+v, said %q", layer, j.Said)
	}
}

// Where main holds no script, what was so stays: the head's, or none.
func TestWhereMainHoldsNoScriptTheHeadsRuns(t *testing.T) {
	tree := aPullRequest(t, map[string]*string{"README.md": s("x")},
		map[string]*string{CheckScript: s("echo 'the first check'; exit 0\n")})
	j, layer := judged(t, tree, "main")
	if layer == nil || layer.Verdict != "pass" || j.Said != "" {
		t.Fatalf("the head's first script answered %+v, said %q", layer, j.Said)
	}
	tree = aPullRequest(t, map[string]*string{"README.md": s("x")}, map[string]*string{"b.md": s("y")})
	if j, _ = judged(t, tree, "main"); j.Script != nil {
		t.Fatalf("neither holds a script, and one judged: %q", j.Script)
	}
	// No base asked (a check by hand without one): the head's, as before.
	tree = aPullRequest(t, map[string]*string{CheckScript: s(mainsCheck)}, map[string]*string{CheckScript: s("exit 0\n")})
	if j, layer = judged(t, tree, ""); layer == nil || layer.Verdict != "pass" {
		t.Fatalf("with no base the head's answered %+v", layer)
	}
}

// A base branch that cannot be read is an error — never a fall back to the change's own script.
func TestABaseThatCannotBeReadIsAnError(t *testing.T) {
	tree := aPullRequest(t, map[string]*string{CheckScript: s(mainsCheck)}, map[string]*string{CheckScript: s("exit 0\n")})
	if _, err := TheCheckThatJudges(t.Context(), tree, "no-such-branch"); err == nil ||
		!strings.Contains(err.Error(), "no-such-branch") {
		t.Fatalf("an unreadable base said %v", err)
	}
}

// The whole check, against a real container runtime: a head without the script fails by main's.
func TestACheckOfAHeadWithoutTheScriptRunsMains(t *testing.T) {
	registry := checkEnvironment(t)
	tree := aPullRequest(t, map[string]*string{CheckScript: s(mainsCheck)}, map[string]*string{CheckScript: nil})
	head, err := gitIn(t.Context(), tree, "rev-parse", "HEAD")
	if err != nil {
		t.Fatal(err)
	}
	origin, err := gitIn(t.Context(), tree, "remote", "get-url", "origin")
	if err != nil {
		t.Fatal(err)
	}
	v, err := Check(t.Context(), Command, CheckSpec{ID: fmt.Sprintf("check-base-%d", time.Now().UnixNano()),
		Repository: strings.TrimSpace(string(origin)), Ref: strings.TrimSpace(string(head)), Owner: "novox",
		Repo: "hq", Base: "main", Toolchain: goToolchain}, t.TempDir(), registry, GitCredential{}, nil)
	if err != nil {
		t.Fatal(err)
	}
	if v.Repo == nil || v.Repo.Verdict != "fail" || !strings.Contains(v.Repo.Summary, "main's judged it") {
		t.Fatalf("a head without the script answered %+v\n%s", v.Repo, v.Report)
	}
}