// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Commercial
// SPDX-FileCopyrightText: 2025-2026 Christian Galo

package httplimit

import (
	"bytes"
	"errors"
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"strings"
	"testing"
)

// closeRecorder wraps a body and records Close, so a test can assert the
// reader closes it on every path.
type closeRecorder struct {
	io.Reader
	closed bool
}

func (c *closeRecorder) Close() error { c.closed = true; return nil }

func response(body string) (*http.Response, *closeRecorder) {
	rec := &closeRecorder{Reader: strings.NewReader(body)}
	u, _ := url.Parse("https://farm.example.test/plugin/farmmanager/sites")
	return &http.Response{StatusCode: 200, Body: rec, Request: &http.Request{URL: u}}, rec
}

func TestReadResponseWithinBoundIsWhole(t *testing.T) {
	resp, rec := response("exactly-32-bytes-of-body-text!!!")
	body, err := ReadResponse(resp, 32)
	if err != nil {
		t.Fatalf("body of bound size must be read whole, got %v", err)
	}
	if string(body) != "exactly-32-bytes-of-body-text!!!" {
		t.Fatalf("body = %q", body)
	}
	if !rec.closed {
		t.Fatal("body must be closed after a successful read")
	}
}

func TestReadResponseOneByteOverIsRefusedNamingBoundAndHost(t *testing.T) {
	resp, rec := response(strings.Repeat("x", 33))
	body, err := ReadResponse(resp, 32)
	if body != nil {
		t.Fatalf("an over-bound response must return no bytes, got %d", len(body))
	}
	var tl *TooLargeError
	if !errors.As(err, &tl) {
		t.Fatalf("want *TooLargeError, got %T %v", err, err)
	}
	if tl.Bound != 32 || tl.Host != "farm.example.test" {
		t.Fatalf("error must name the bound and the host, got %+v", tl)
	}
	if !strings.Contains(err.Error(), "farm.example.test") || !strings.Contains(err.Error(), "32 bytes") {
		t.Fatalf("message must name host and bound: %q", err.Error())
	}
	if !IsTooLarge(err) {
		t.Fatal("IsTooLarge must recognise its own error")
	}
	if !rec.closed {
		t.Fatal("body must be closed after a refusal")
	}
}

// The reader never asks for more than max+1 bytes, so a stream with no end
// costs one byte over the bound, not the stream.
func TestReadResponseStopsReadingAtTheBound(t *testing.T) {
	endless := &countingReader{}
	u, _ := url.Parse("http://forum.example.test/")
	resp := &http.Response{Body: io.NopCloser(endless), Request: &http.Request{URL: u}}
	if _, err := ReadResponse(resp, 1024); !IsTooLarge(err) {
		t.Fatalf("want TooLargeError, got %v", err)
	}
	if endless.n > 1024+1 {
		t.Fatalf("read %d bytes from an endless body; the bound plus one is the ceiling", endless.n)
	}
}

type countingReader struct{ n int64 }

func (c *countingReader) Read(p []byte) (int, error) {
	for i := range p {
		p[i] = 'y'
	}
	c.n += int64(len(p))
	return len(p), nil
}

func TestDecodeResponse(t *testing.T) {
	t.Run("a document within the bound decodes", func(t *testing.T) {
		resp, _ := response(`{"name":"a"}`)
		var v struct{ Name string }
		if err := DecodeResponse(resp, DefaultResponseBytes, &v); err != nil || v.Name != "a" {
			t.Fatalf("decode: %v, %+v", err, v)
		}
	})
	t.Run("a document over the bound is refused, not truncated", func(t *testing.T) {
		resp, _ := response(`{"name":"` + strings.Repeat("a", 64) + `"}`)
		var v struct{ Name string }
		err := DecodeResponse(resp, 32, &v)
		if !IsTooLarge(err) {
			t.Fatalf("want TooLargeError, got %v", err)
		}
		if v.Name != "" {
			t.Fatal("nothing must be decoded from a refused body")
		}
	})
}

// Against a live server: the bound holds for a real body on the wire, and
// the host in the error is the one the request went to.
func TestReadResponseAgainstServer(t *testing.T) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = w.Write(bytes.Repeat([]byte("z"), 4096))
	}))
	defer srv.Close()
	resp, err := http.Get(srv.URL)
	if err != nil {
		t.Fatal(err)
	}
	_, err = ReadResponse(resp, 1000)
	var tl *TooLargeError
	if !errors.As(err, &tl) || tl.Host != strings.TrimPrefix(srv.URL, "http://") {
		t.Fatalf("want TooLargeError for %s, got %v", srv.URL, err)
	}
}