package symlinks

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

// testRequired returns a SharedSymlink list whose Targets live entirely
// under tmpDir, so the tests never touch the operator's real home.
func testRequired(tmpDir string) []SharedSymlink {
	return []SharedSymlink{
		{Target: filepath.Join(tmpDir, "session-env-shared"), Name: "session-env"},
		{Target: filepath.Join(tmpDir, "file-history-shared"), Name: "file-history"},
		{Target: filepath.Join(tmpDir, "projects-shared"), Name: "projects"},
	}
}

func TestEnsureForAccount_missingCreatesLinksAndTargets(t *testing.T) {
	tmp := t.TempDir()
	home := filepath.Join(tmp, "account1")
	req := testRequired(tmp)

	if err := EnsureForAccount(home, req); err != nil {
		t.Fatalf("EnsureForAccount: %v", err)
	}

	for _, sl := range req {
		linkPath := filepath.Join(home, sl.Name)
		info, err := os.Lstat(linkPath)
		if err != nil {
			t.Errorf("expected link at %s: %v", linkPath, err)
			continue
		}
		if info.Mode()&os.ModeSymlink == 0 {
			t.Errorf("%s exists but is not a symlink", linkPath)
		}
		got, err := os.Readlink(linkPath)
		if err != nil {
			t.Errorf("readlink %s: %v", linkPath, err)
			continue
		}
		if got != sl.Target {
			t.Errorf("link %s points to %q, want %q", linkPath, got, sl.Target)
		}
		// Target directory must exist too.
		if st, err := os.Stat(sl.Target); err != nil || !st.IsDir() {
			t.Errorf("target %s should be a directory, err=%v", sl.Target, err)
		}
	}
}

func TestEnsureForAccount_idempotent(t *testing.T) {
	tmp := t.TempDir()
	home := filepath.Join(tmp, "account1")
	req := testRequired(tmp)

	if err := EnsureForAccount(home, req); err != nil {
		t.Fatalf("first pass: %v", err)
	}
	if err := EnsureForAccount(home, req); err != nil {
		t.Fatalf("second pass should be a no-op, got: %v", err)
	}
}

func TestEnsureForAccount_divergentLinkReturnsError(t *testing.T) {
	tmp := t.TempDir()
	home := filepath.Join(tmp, "account1")
	req := testRequired(tmp)

	// Pre-create a wrong symlink for "projects".
	if err := os.MkdirAll(home, 0700); err != nil {
		t.Fatalf("mkdir home: %v", err)
	}
	wrongTarget := filepath.Join(tmp, "someone-elses-dir")
	if err := os.MkdirAll(wrongTarget, 0700); err != nil {
		t.Fatalf("mkdir wrong target: %v", err)
	}
	linkPath := filepath.Join(home, "projects")
	if err := os.Symlink(wrongTarget, linkPath); err != nil {
		t.Fatalf("seed wrong symlink: %v", err)
	}

	err := EnsureForAccount(home, req)
	if err == nil {
		t.Fatal("expected error for divergent link, got nil")
	}
	if !strings.Contains(err.Error(), "divergent") {
		t.Errorf("error should mention 'divergent': %v", err)
	}

	// The wrong symlink MUST be preserved (no auto-correction).
	got, err := os.Readlink(linkPath)
	if err != nil {
		t.Fatalf("readlink after error: %v", err)
	}
	if got != wrongTarget {
		t.Errorf("divergent link was mutated: now %q, want preserved %q", got, wrongTarget)
	}
}

func TestEnsureForAccount_regularFileInsteadOfLinkFails(t *testing.T) {
	tmp := t.TempDir()
	home := filepath.Join(tmp, "account1")
	req := testRequired(tmp)

	if err := os.MkdirAll(home, 0700); err != nil {
		t.Fatalf("mkdir home: %v", err)
	}
	// Create a regular file at the session-env path.
	bogus := filepath.Join(home, "session-env")
	if err := os.WriteFile(bogus, []byte("oops"), 0600); err != nil {
		t.Fatalf("seed regular file: %v", err)
	}

	err := EnsureForAccount(home, req)
	if err == nil {
		t.Fatal("expected error for regular-file-at-link-path, got nil")
	}
	if !strings.Contains(err.Error(), "not a symlink") {
		t.Errorf("error should mention 'not a symlink': %v", err)
	}
}

func TestEnsureForAccount_emptyHomeReturnsError(t *testing.T) {
	if err := EnsureForAccount("", nil); err == nil {
		t.Fatal("expected error for empty home, got nil")
	}
}

func TestValidateAll_multipleAccountsAllOK(t *testing.T) {
	tmp := t.TempDir()
	req := testRequired(tmp)
	homes := []string{
		filepath.Join(tmp, "a"),
		filepath.Join(tmp, "b"),
	}
	if err := ValidateAll(homes, req); err != nil {
		t.Fatalf("ValidateAll: %v", err)
	}
}

func TestValidateAll_aggregatesErrors(t *testing.T) {
	tmp := t.TempDir()
	req := testRequired(tmp)
	homes := []string{
		filepath.Join(tmp, "a"),
		filepath.Join(tmp, "b"),
	}

	// Pre-seed account `a` with a divergent link so ValidateAll must
	// surface that error while still processing account `b`.
	if err := os.MkdirAll(homes[0], 0700); err != nil {
		t.Fatalf("mkdir a: %v", err)
	}
	wrongTarget := filepath.Join(tmp, "bad")
	if err := os.MkdirAll(wrongTarget, 0700); err != nil {
		t.Fatalf("mkdir bad: %v", err)
	}
	if err := os.Symlink(wrongTarget, filepath.Join(homes[0], "projects")); err != nil {
		t.Fatalf("seed wrong link: %v", err)
	}

	err := ValidateAll(homes, req)
	if err == nil {
		t.Fatal("expected aggregated error, got nil")
	}
	if !strings.Contains(err.Error(), "divergent") {
		t.Errorf("should surface divergent: %v", err)
	}

	// Account `b` must have been configured successfully even though `a`
	// failed. Otherwise the operator cannot see the full state at once.
	for _, sl := range req {
		if _, err := os.Lstat(filepath.Join(homes[1], sl.Name)); err != nil {
			t.Errorf("account b link %s should have been created despite a's failure: %v", sl.Name, err)
		}
	}
}

func TestValidateAll_emptyListReturnsError(t *testing.T) {
	if err := ValidateAll(nil, nil); err == nil {
		t.Fatal("expected error for empty account list")
	}
}

// TestRequiredShared_defaultsAreReasonable pins the default SharedSymlink
// list so an accidental edit that breaks production is caught.
func TestRequiredShared_defaultsAreReasonable(t *testing.T) {
	want := map[string]string{
		"session-env":  "/home/ubuntu/.claude-session-env-shared",
		"file-history": "/home/ubuntu/.claude-file-history-shared",
		"projects":     "/home/ubuntu/.claude-projects-shared",
	}
	if len(RequiredShared) != len(want) {
		t.Fatalf("RequiredShared has %d entries, want %d", len(RequiredShared), len(want))
	}
	for _, sl := range RequiredShared {
		if got, ok := want[sl.Name]; !ok {
			t.Errorf("unexpected RequiredShared entry %q", sl.Name)
		} else if got != sl.Target {
			t.Errorf("RequiredShared %q target = %q, want %q", sl.Name, sl.Target, got)
		}
	}
}