package responseheaders

import (
	"net/http"
	"testing"

	"github.com/user-management-system/internal/config"
)

func TestFilterHeadersDisabledUsesDefaultAllowlist(t *testing.T) {
	src := http.Header{}
	src.Add("Content-Type", "application/json")
	src.Add("X-Request-Id", "req-123")
	src.Add("X-Test", "ok")
	src.Add("Connection", "keep-alive")
	src.Add("Content-Length", "123")

	cfg := config.ResponseHeaderConfig{
		Enabled:     false,
		ForceRemove: []string{"x-request-id"},
	}

	filtered := FilterHeaders(src, CompileHeaderFilter(cfg))
	if filtered.Get("Content-Type") != "application/json" {
		t.Fatalf("expected Content-Type passthrough, got %q", filtered.Get("Content-Type"))
	}
	if filtered.Get("X-Request-Id") != "req-123" {
		t.Fatalf("expected X-Request-Id allowed, got %q", filtered.Get("X-Request-Id"))
	}
	if filtered.Get("X-Test") != "" {
		t.Fatalf("expected X-Test removed, got %q", filtered.Get("X-Test"))
	}
	if filtered.Get("Connection") != "" {
		t.Fatalf("expected Connection to be removed, got %q", filtered.Get("Connection"))
	}
	if filtered.Get("Content-Length") != "" {
		t.Fatalf("expected Content-Length to be removed, got %q", filtered.Get("Content-Length"))
	}
}

func TestFilterHeadersEnabledUsesAllowlist(t *testing.T) {
	src := http.Header{}
	src.Add("Content-Type", "application/json")
	src.Add("X-Extra", "ok")
	src.Add("X-Remove", "nope")
	src.Add("X-Blocked", "nope")

	cfg := config.ResponseHeaderConfig{
		Enabled:           true,
		AdditionalAllowed: []string{"x-extra"},
		ForceRemove:       []string{"x-remove"},
	}

	filtered := FilterHeaders(src, CompileHeaderFilter(cfg))
	if filtered.Get("Content-Type") != "application/json" {
		t.Fatalf("expected Content-Type allowed, got %q", filtered.Get("Content-Type"))
	}
	if filtered.Get("X-Extra") != "ok" {
		t.Fatalf("expected X-Extra allowed, got %q", filtered.Get("X-Extra"))
	}
	if filtered.Get("X-Remove") != "" {
		t.Fatalf("expected X-Remove removed, got %q", filtered.Get("X-Remove"))
	}
	if filtered.Get("X-Blocked") != "" {
		t.Fatalf("expected X-Blocked removed, got %q", filtered.Get("X-Blocked"))
	}
}

func TestFilterHeadersNilFilter(t *testing.T) {
	src := http.Header{}
	src.Add("Content-Type", "application/json")
	src.Add("X-Request-Id", "req-123")
	src.Add("X-Unknown", "unknown")

	// nil filter should use default compiled filter
	filtered := FilterHeaders(src, nil)
	if filtered.Get("Content-Type") != "application/json" {
		t.Fatalf("expected Content-Type allowed, got %q", filtered.Get("Content-Type"))
	}
	if filtered.Get("X-Request-Id") != "req-123" {
		t.Fatalf("expected X-Request-Id allowed, got %q", filtered.Get("X-Request-Id"))
	}
	if filtered.Get("X-Unknown") != "" {
		t.Fatalf("expected X-Unknown removed, got %q", filtered.Get("X-Unknown"))
	}
}

func TestCompileHeaderFilterEmptyStrings(t *testing.T) {
	cfg := config.ResponseHeaderConfig{
		Enabled:           true,
		AdditionalAllowed: []string{"", "  ", "valid"},
		ForceRemove:       []string{"", "  "},
	}

	filter := CompileHeaderFilter(cfg)
	if filter == nil {
		t.Fatal("expected filter to be created")
	}

	// Empty strings should be filtered out
	src := http.Header{}
	src.Add("Valid", "value")
	filtered := FilterHeaders(src, filter)
	if filtered.Get("Valid") != "value" {
		t.Fatalf("expected Valid header to pass through")
	}
}

func TestWriteFilteredHeaders(t *testing.T) {
	src := http.Header{}
	src.Add("Content-Type", "application/json")
	src.Add("X-Custom", "custom")

	dst := http.Header{}
	WriteFilteredHeaders(dst, src, nil)

	if dst.Get("Content-Type") != "application/json" {
		t.Fatalf("expected Content-Type written to dst")
	}
	if dst.Get("X-Custom") != "" {
		t.Fatalf("expected X-Custom filtered out")
	}
}

func TestFilterHeadersMultipleValues(t *testing.T) {
	src := http.Header{}
	src.Add("Content-Type", "application/json")
	src.Add("Vary", "Accept")
	src.Add("Vary", "Accept-Encoding")

	filtered := FilterHeaders(src, nil)
	varyValues := filtered["Vary"]
	if len(varyValues) != 2 {
		t.Fatalf("expected 2 Vary values, got %d", len(varyValues))
	}
}