package metrics

import (
	"errors"
	"net/http"
	"net/http/httptest"
	"testing"

	"github.com/labstack/echo/v5"
	echoMiddleware "github.com/labstack/echo/v5/middleware"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/testutil"
	dto "github.com/prometheus/client_model/go"
	"github.com/stretchr/testify/assert"
)

func newEcho() *echo.Echo {
	e := echo.New()
	e.Use(Middleware())
	e.Use(echoMiddleware.Recover())
	e.GET("/items/:id", func(c *echo.Context) error { return c.String(http.StatusOK, "item") })
	e.GET("/fail", func(c *echo.Context) error { return errors.New("broken") })
	e.GET("/panic", func(c *echo.Context) error { panic("boom") })
	return e
}

func serve(e *echo.Echo, method, target string) {
	e.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest(method, target, nil))
}

func requests(method, route, code string) float64 {
	return testutil.ToFloat64(httpRequests.WithLabelValues(method, route, code))
}

func TestMiddlewareCountsRequestsByRoutePattern(t *testing.T) {
	e := newEcho()
	before := requests("GET", "/items/:id", "200")

	serve(e, http.MethodGet, "/items/1?x=secret")
	serve(e, http.MethodGet, "/items/2")

	assert.Equal(t, before+2, requests("GET", "/items/:id", "200"))
	assert.Equal(t, 0.0, requests("GET", "/items/1?x=secret", "200"), "the URL is never a label")
	assert.Equal(t, 0.0, requests("GET", "/items/1", "200"))
}

func TestMiddlewareRecordsErrorStatus(t *testing.T) {
	e := newEcho()
	failBefore := requests("GET", "/fail", "500")
	panicBefore := requests("GET", "/panic", "500")
	missingBefore := requests("GET", unmatchedRoute, "404")

	serve(e, http.MethodGet, "/fail")
	serve(e, http.MethodGet, "/panic")
	serve(e, http.MethodGet, "/no/such/page?q=1")

	assert.Equal(t, failBefore+1, requests("GET", "/fail", "500"))
	assert.Equal(t, panicBefore+1, requests("GET", "/panic", "500"), "Recover turns the panic into a 500")
	assert.Equal(t, missingBefore+1, requests("GET", unmatchedRoute, "404"))
}

func observations(method, route string) uint64 {
	m := &dto.Metric{}
	_ = httpDuration.WithLabelValues(method, route).(prometheus.Metric).Write(m)
	return m.GetHistogram().GetSampleCount()
}

func TestMiddlewareRecordsLatency(t *testing.T) {
	e := newEcho()
	before := observations("GET", "/items/:id")

	serve(e, http.MethodGet, "/items/1")

	assert.Equal(t, before+1, observations("GET", "/items/:id"))
}