package tool

import (
	"context"
	"net"
	"strings"
	"testing"
)

// TestResolveAndCheck_AllowlistedPublic anchors the happy path: a
// public domain in the allowlist resolves and returns its IP. Skips
// when DNS isn't available so the suite still passes in offline CI.
func TestResolveAndCheck_AllowlistedPublic(t *testing.T) {
	// Pre-flight: skip the test if the test environment has no DNS.
	if _, err := net.LookupHost("example.com"); err != nil {
		t.Skipf("no DNS in test environment: %v", err)
	}
	allow := AllowlistConfig{Domains: []string{"example.com"}}
	ip, err := ResolveAndCheck(context.Background(), "https://example.com/", allow)
	if err != nil {
		t.Fatalf("ResolveAndCheck failed: %v", err)
	}
	if ip == nil {
		t.Fatal("expected non-nil IP")
	}
}

// TestResolveAndCheck_NotAllowlisted ensures a domain outside the
// allowlist is rejected before any DNS resolution.
func TestResolveAndCheck_NotAllowlisted(t *testing.T) {
	allow := AllowlistConfig{Domains: []string{"example.com"}}
	_, err := ResolveAndCheck(context.Background(), "https://evil.test/", allow)
	if err == nil {
		t.Fatal("expected rejection for non-allowlisted host")
	}
	if !strings.Contains(err.Error(), "not in allowlist") {
		t.Errorf("expected allowlist error, got: %v", err)
	}
}

// TestResolveAndCheck_WildcardMatch confirms "*.example.com" matches
// foo.example.com.
func TestResolveAndCheck_WildcardMatch(t *testing.T) {
	if !matchesAllowlist("foo.example.com", []string{"*.example.com"}) {
		t.Error("expected *.example.com to match foo.example.com")
	}
	if !matchesAllowlist("a.b.example.com", []string{"*.example.com"}) {
		t.Error("expected *.example.com to match a.b.example.com")
	}
}

// TestResolveAndCheck_WildcardDoesNotMatchBareDomain documents the
// design choice: "*.example.com" does NOT match "example.com" itself.
// Admins who want both must list both entries.
func TestResolveAndCheck_WildcardDoesNotMatchBareDomain(t *testing.T) {
	if matchesAllowlist("example.com", []string{"*.example.com"}) {
		t.Error("expected *.example.com NOT to match bare example.com")
	}
}

// TestResolveAndCheck_LocalhostRejected verifies that a hostname
// resolving to 127.0.0.1 is rejected unless the admin explicitly
// includes it in the allowlist.
func TestResolveAndCheck_LocalhostRejected(t *testing.T) {
	if _, err := net.LookupHost("localhost"); err != nil {
		t.Skipf("no DNS in test environment: %v", err)
	}
	// "localhost" matches the allowlist by exact name match, but the
	// hostExplicitlyAllowed bypass kicks in only when the host is in
	// the allowlist as an exact entry. Here we use a DIFFERENT bare
	// allowlist entry so the host fails the allowlist match outright.
	allow := AllowlistConfig{Domains: []string{"example.com"}}
	_, err := ResolveAndCheck(context.Background(), "http://localhost/", allow)
	if err == nil {
		t.Fatal("expected rejection for localhost (not in allowlist)")
	}
}

// TestResolveAndCheck_LocalhostAllowedExplicit confirms the
// admin-opt-in escape hatch: when the hostname is itself in the
// allowlist as an exact entry, the private-IP check is bypassed.
// This is what test code uses to drive httptest.NewServer URLs.
func TestResolveAndCheck_LocalhostAllowedExplicit(t *testing.T) {
	// Use 127.0.0.1 directly so this test doesn't depend on DNS for
	// "localhost".
	allow := AllowlistConfig{Domains: []string{"127.0.0.1"}}
	ip, err := ResolveAndCheck(context.Background(), "http://127.0.0.1/", allow)
	if err != nil {
		t.Fatalf("expected 127.0.0.1 with explicit allowlist to succeed; got: %v", err)
	}
	if !ip.Equal(net.ParseIP("127.0.0.1")) {
		t.Errorf("expected ip=127.0.0.1, got %v", ip)
	}
}

// TestResolveAndCheck_FileSchemeRejected blocks file:// URLs.
func TestResolveAndCheck_FileSchemeRejected(t *testing.T) {
	allow := AllowlistConfig{Domains: []string{"anything"}}
	_, err := ResolveAndCheck(context.Background(), "file:///etc/passwd", allow)
	if err == nil {
		t.Fatal("expected rejection for file:// scheme")
	}
	if !strings.Contains(err.Error(), "scheme") {
		t.Errorf("expected scheme error, got: %v", err)
	}
}

// TestResolveAndCheck_EmptyHostRejected blocks malformed URLs with
// no host component.
func TestResolveAndCheck_EmptyHostRejected(t *testing.T) {
	allow := AllowlistConfig{Domains: []string{"anything"}}
	_, err := ResolveAndCheck(context.Background(), "http:///nohost", allow)
	if err == nil {
		t.Fatal("expected rejection for empty host")
	}
}

// TestResolveAndCheck_PrivateIPLiteralRejected confirms that an IP
// literal resolving to the private range is rejected even if the
// allowlist matches by wildcard or other means. The private-IP gate
// is the last line of defence.
func TestResolveAndCheck_PrivateIPLiteralRejected(t *testing.T) {
	// Add a wildcard that would match anything (silly but plausible
	// admin error) and confirm a private IP literal is still blocked
	// because the literal isn't itself in the allowlist as exact.
	allow := AllowlistConfig{Domains: []string{"192.168.1.1"}}
	// The exact-IP-in-allowlist case bypasses the private check; flip
	// to a NEAR-but-different IP literal that's NOT in the allowlist.
	allow2 := AllowlistConfig{Domains: []string{"192.168.0.0"}}
	_, err := ResolveAndCheck(context.Background(), "http://192.168.1.1/", allow2)
	if err == nil {
		t.Fatal("expected rejection for private IP literal not in allowlist")
	}
	// Sanity: explicit allowlist entry bypasses.
	_, err = ResolveAndCheck(context.Background(), "http://192.168.1.1/", allow)
	if err != nil {
		t.Errorf("expected explicit allowlist entry to bypass; got: %v", err)
	}
}

// TestResolveAndCheck_CloudMetadataRejected blocks the well-known
// cloud metadata IP via the link-local check. We use a wildcard that
// matches the IP-as-hostname so the rejection comes from the
// private/link-local layer (not the allowlist).
func TestResolveAndCheck_CloudMetadataRejected(t *testing.T) {
	// "*.169.254.169.254" wildcard wouldn't match either; instead use
	// a wildcard that matches any IP literal under .254 — but
	// matchesAllowlist treats '.' as a literal so we just allowlist
	// the IP itself with a one-bit-different sibling that fails the
	// exact-allow check (so private check still runs).
	//
	// Easier: include a different exact IP entry so the IP literal
	// fails hostExplicitlyAllowed but passes the wildcard.
	allow := AllowlistConfig{Domains: []string{"*.169.254.169.254"}} // matches "x.169.254.169.254", not the bare IP
	// 169.254.169.254 won't match the wildcard pattern either —
	// switch to a strategy that lets the host pass allowlist but
	// fails the private check.
	_ = allow
	// Use an explicit non-IP-literal hostname (we'd need DNS to point
	// to 169.254.169.254 which is not feasible). Instead, exercise
	// the rejectPrivateIP helper directly for the metadata IP since
	// the public surface only enters that path through resolution.
	if err := rejectPrivateIP("metadata.test", net.ParseIP("169.254.169.254")); err == nil {
		t.Fatal("expected rejection for cloud metadata IP")
	} else if !strings.Contains(err.Error(), "metadata") {
		t.Errorf("expected metadata error, got: %v", err)
	}
}