package link

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

// Where the conformance fixtures are read from, held on a small SDK repository of the test's own: two
// commits, the clone checked out at the older as the build seat leaves it at the running controller's pin
// (novox/hq issue 449). The contents are the test's, because what is judged is which commit is read.
type sdkBed struct {
	root, goMod, captured, capturedLog string
	older, newer                       string
}

const fixtureName = "events/module-event.json"

func newSDKBed(t *testing.T) sdkBed {
	t.Helper()
	if _, err := exec.LookPath("git"); err != nil {
		t.Fatalf("git is needed to read the SDK at a pin, as a merge check does: %v", err)
	}
	b := sdkBed{root: t.TempDir()}
	clone := filepath.Join(b.root, "mesh-sdk")
	git := func(args ...string) string {
		t.Helper()
		cmd := exec.Command("git", append([]string{"-C", clone, "-c", "user.name=t", "-c", "user.email=t@t",
			"-c", "commit.gpgsign=false"}, args...)...)
		out, err := cmd.CombinedOutput()
		if err != nil {
			t.Fatalf("git %v: %v: %s", args, err, out)
		}
		return strings.TrimSpace(string(out))
	}
	write := func(dir, body string) {
		t.Helper()
		file := filepath.Join(dir, "conformance", filepath.FromSlash(fixtureName))
		if err := os.MkdirAll(filepath.Dir(file), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(file, []byte(body), 0o644); err != nil {
			t.Fatal(err)
		}
	}
	if err := os.MkdirAll(clone, 0o755); err != nil {
		t.Fatal(err)
	}
	git("init", "--quiet")
	write(clone, "older\n")
	git("add", "-A")
	git("commit", "--quiet", "-m", "older")
	b.older = git("rev-parse", "HEAD")
	write(clone, "newer\n")
	git("commit", "--quiet", "-am", "newer")
	b.newer = git("rev-parse", "HEAD")
	git("checkout", "--quiet", b.older)

	other := t.TempDir()
	b.captured = filepath.Join(other, "mesh-sdk")
	write(b.captured, "older\n")
	b.capturedLog = filepath.Join(other, "CAPTURED")
	if err := os.WriteFile(b.capturedLog, []byte("mesh-sdk  "+b.older+"  conformance/events\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	b.goMod = filepath.Join(other, "go.mod")
	b.pin(t, b.newer)
	return b
}

func (b sdkBed) pin(t *testing.T, commit string) {
	t.Helper()
	mod := "module x\n\nrequire (\n\t" + sdkModule + " v0.1.11-0.20261009143344-" + commit[:12] + "\n)\n"
	if err := os.WriteFile(b.goMod, []byte(mod), 0o644); err != nil {
		t.Fatal(err)
	}
}

// A pull request moving the SDK is judged against the SDK it moves to: the clone is read at the tree's own
// pin, not at what it is checked out at, the running controller's.
func TestAMergeCheckReadsTheSDKAtTheTreesOwnPin(t *testing.T) {
	b := newSDKBed(t)
	raw, from, err := sdkFixture(b.root, b.goMod, b.captured, b.capturedLog, fixtureName)
	if err != nil {
		t.Fatal(err)
	}
	if string(raw) != "newer\n" {
		t.Errorf("read %q from %s; the tree pins the newer commit", raw, from)
	}
}

// A captured copy that is not the SDK's at the commit CAPTURED names fails a merge check.
func TestAMergeCheckFailsACapturedCopyEditedByHand(t *testing.T) {
	b := newSDKBed(t)
	if err := os.WriteFile(filepath.Join(b.captured, "conformance", filepath.FromSlash(fixtureName)),
		[]byte("edited\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	if _, _, err := sdkFixture(b.root, b.goMod, b.captured, b.capturedLog, fixtureName); err == nil ||
		!strings.Contains(err.Error(), "is not mesh-sdk's at") {
		t.Errorf("a hand-edited captured copy was accepted: %v", err)
	}
}

// A pin the clone does not hold fails loudly and names it.
func TestAMergeCheckFailsWithoutTheSDKAtItsPin(t *testing.T) {
	b := newSDKBed(t)
	b.pin(t, "0123456789ab0123456789ab0123456789ab0123")
	if _, _, err := sdkFixture(b.root, b.goMod, b.captured, b.capturedLog, fixtureName); err == nil ||
		!strings.Contains(err.Error(), "0123456789ab") {
		t.Errorf("a pin the clone lacks was not named: %v", err)
	}
}

// Until mesh-controller #220 has rolled out the seat places no mesh-sdk beside a check: the captured copy is
// read, and where it was read from says plainly that the clone did not judge it (novox/hq issue 449).
func TestAMergeCheckWithoutTheCloneSaysItReadTheCapturedCopy(t *testing.T) {
	b := newSDKBed(t)
	raw, from, err := sdkFixture(t.TempDir(), b.goMod, b.captured, b.capturedLog, fixtureName)
	if err != nil || string(raw) != "older\n" {
		t.Fatalf("read %q, %v; the captured copy holds the older", raw, err)
	}
	if !strings.HasPrefix(from, "NOT JUDGED AGAINST THE CLONE") || !strings.Contains(from, b.older) {
		t.Errorf("the log does not say the clone was missing and which copy was read: %q", from)
	}
}

// Away from a merge check the captured copy is read, and nothing else.
func TestAwayFromACheckTheCapturedCopyIsRead(t *testing.T) {
	b := newSDKBed(t)
	raw, _, err := sdkFixture("", b.goMod, b.captured, b.capturedLog, fixtureName)
	if err != nil || string(raw) != "older\n" {
		t.Errorf("read %q, %v; the captured copy holds the older", raw, err)
	}
}