package main

import (
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"strings"
	"testing"
	"testing/iotest"
)

func snapshotResponse(target, body string) *http.Response {
	request, _ := http.NewRequest(http.MethodGet, target, nil)
	return &http.Response{
		StatusCode: http.StatusOK,
		Header:     make(http.Header),
		Body:       io.NopCloser(strings.NewReader(body)),
		Request:    request,
	}
}

func TestBoundSessionSnapshotKeepsOnlyRecentMessages(t *testing.T) {
	messages := make([]map[string]int, 30)
	for index := range messages {
		messages[index] = map[string]int{"index": index}
	}
	body, _ := json.Marshal(map[string]any{
		"session_id": "resolved", "messages": messages,
	})
	response := snapshotResponse(
		"http://tenant/api/sessions/root/messages?limit=24&hermes_fallback=1",
		string(body),
	)
	response.Header.Set("ETag", "stale")
	if err := boundSessionSnapshot(response); err != nil {
		t.Fatal(err)
	}
	var bounded sessionSnapshot
	if err := json.NewDecoder(response.Body).Decode(&bounded); err != nil {
		t.Fatal(err)
	}
	if len(bounded.Messages) != 24 || bounded.TotalMessages != 30 {
		t.Fatalf("snapshot was not bounded: %#v", bounded)
	}
	var first map[string]int
	if err := json.Unmarshal(bounded.Messages[0], &first); err != nil || first["index"] != 6 {
		t.Fatalf("snapshot did not retain the recent tail: %#v, %v", first, err)
	}
	if response.Header.Get("Cache-Control") != "no-store" || response.Header.Get("ETag") != "" {
		t.Fatal("bounded snapshot retained cache metadata")
	}
}

func TestBoundSessionSnapshotPreservesLargerReportedTotal(t *testing.T) {
	response := snapshotResponse(
		"http://tenant/api/sessions/root/messages?hermes_fallback=1",
		`{"session_id":"leaf","messages":[],"total_messages":100}`,
	)
	if err := boundSessionSnapshot(response); err != nil {
		t.Fatal(err)
	}
	var bounded sessionSnapshot
	if err := json.NewDecoder(response.Body).Decode(&bounded); err != nil {
		t.Fatal(err)
	}
	if bounded.SessionID != "leaf" || bounded.TotalMessages != 100 {
		t.Fatalf("reported total was lost: %#v", bounded)
	}
}

func TestBoundSessionSnapshotFailsClosedOnMalformedOrOversizedBody(t *testing.T) {
	for name, body := range map[string]string{
		"malformed": `{`,
		"oversized": strings.Repeat("x", sessionSnapshotBytes+1),
	} {
		t.Run(name, func(t *testing.T) {
			response := snapshotResponse(
				"http://tenant/api/sessions/root/messages?hermes_fallback=1",
				body,
			)
			if err := boundSessionSnapshot(response); err == nil {
				t.Fatal("unsafe snapshot was accepted")
			}
		})
	}
	response := snapshotResponse(
		"http://tenant/api/sessions/root/messages?hermes_fallback=1", `{}`,
	)
	response.Body = io.NopCloser(iotest.ErrReader(errors.New("read failed")))
	if err := boundSessionSnapshot(response); err == nil {
		t.Fatal("snapshot body read failure was ignored")
	}
}

func TestBoundSessionSnapshotLeavesNativeAndErrorResponsesUntouched(t *testing.T) {
	for _, response := range []*http.Response{
		{StatusCode: http.StatusOK},
		snapshotResponse("http://tenant/api/sessions/root/messages", `{}`),
		snapshotResponse("http://tenant/api/sessions/root", `{}`),
	} {
		if err := boundSessionSnapshot(response); err != nil {
			t.Fatal(err)
		}
	}
	errorResponse := snapshotResponse(
		"http://tenant/api/sessions/root/messages?hermes_fallback=1", `{}`,
	)
	errorResponse.StatusCode = http.StatusNotFound
	if err := boundSessionSnapshot(errorResponse); err != nil {
		t.Fatal(err)
	}
}