// Copyright 2015 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package tumble

import (
	"context"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"time"

	"go.chromium.org/luci/common/clock"
	"go.chromium.org/luci/common/clock/testclock"
	"go.chromium.org/luci/common/data/rand/cryptorand"
	"go.chromium.org/luci/common/logging"
	"go.chromium.org/luci/common/logging/memlogger"
	"go.chromium.org/luci/server/router"
	"go.chromium.org/luci/server/settings"

	"go.chromium.org/luci/gae/impl/memory"
	ds "go.chromium.org/luci/gae/service/datastore"
	"go.chromium.org/luci/gae/service/info"
	tq "go.chromium.org/luci/gae/service/taskqueue"
)

// Testing is a high-level testing object for testing applications that use
// tumble.
type Testing struct {
	Service
}

// UpdateSettings changes the tumble settings in the context to match cfg.
//
// If cfg == nil, this resets the settings to their default values.
func (t *Testing) UpdateSettings(c context.Context, cfg *Config) {
	if cfg == nil {
		dflt := defaultConfig
		dflt.DustSettleTimeout = 0
		cfg = &dflt
	}
	settings.Set(c, baseName, cfg, "tumble.Testing", "for testing")
}

// GetConfig retrieves the current tumble settings
func (t *Testing) GetConfig(c context.Context) *Config {
	return getConfig(c)
}

// Context generates a correctly configured context with:
//   * luci/gae/impl/memory
//   * luci/luci-go/common/clock/testclock
//   * luci/luci-go/common/logging/memlogger
//   * luci/luci-go/server/settings (MemoryStorage)
//
// It also correctly configures the "tumble.Mutation" indexes and taskqueue
// named in this Testing config.
func (t *Testing) Context() context.Context {
	ctx := memory.Use(memlogger.Use(context.Background()))
	ctx, _ = testclock.UseTime(ctx, testclock.TestTimeUTC.Round(time.Millisecond))
	ctx = settings.Use(ctx, settings.New(&settings.MemoryStorage{}))
	ctx = cryptorand.MockForTest(ctx, 765589025) // as chosen by fair dice roll
	t.UpdateSettings(ctx, nil)

	tq.GetTestable(ctx).CreateQueue(baseName)

	ds.GetTestable(ctx).AddIndexes(&ds.IndexDefinition{
		Kind: "tumble.Mutation",
		SortBy: []ds.IndexColumn{
			{Property: "ExpandedShard"},
			{Property: "TargetRoot"},
		},
	})
	ds.GetTestable(ctx).Consistent(true)

	return ctx
}

// EnableDelayedMutations turns on delayed mutations for this context.
func (t *Testing) EnableDelayedMutations(c context.Context) {
	cfg := t.GetConfig(c)
	if !cfg.DelayedMutations {
		cfg.DelayedMutations = true
		ds.GetTestable(c).AddIndexes(&ds.IndexDefinition{
			Kind: "tumble.Mutation",
			SortBy: []ds.IndexColumn{
				{Property: "TargetRoot"},
				{Property: "ProcessAfter"},
			},
		})
		t.UpdateSettings(c, cfg)
	}
}

// Iterate makes a single iteration of the tumble service worker, and returns
// the number of shards that were processed. Iterate operates on the Context's
// current namespace.
//
// It will skip all work items if the test clock hasn't advanced in time
// enough.
func (t *Testing) Iterate(c context.Context) int {
	clk := clock.Get(c).(testclock.TestClock)
	logging.Debugf(c, "tumble.Testing.Iterate: time(%d|%s)", timestamp(clk.Now().Unix()), clk.Now().UTC())

	r := router.New()
	t.InstallHandlers(r, nil)

	ret := 0
	tsks := tq.GetTestable(c).GetScheduledTasks()[baseName]
	logging.Debugf(c, "got tasks: %v", tsks)
	for _, tsk := range tsks {
		logging.Debugf(c, "found task: %v", tsk)
		if tsk.ETA.After(clk.Now().UTC()) {
			logging.Infof(c, "skipping task: ETA(%s): %s", tsk.ETA, tsk.Path)
			continue
		}

		req, err := http.NewRequest("POST", tsk.Path, nil)
		if err != nil {
			panic(err)
		}
		req.Header.Set("X-AppEngine-QueueName", baseName)

		// Determine our parameters.
		params, ok := r.GetParams("POST", req.URL.Path)
		if !ok {
			panic(fmt.Errorf("failed to lookup path: %s", req.URL.Path))
		}

		// Process the shard until a success or hard failure.
		retryHTTP(c, func(rec *httptest.ResponseRecorder) {
			t.ProcessShardHandler(&router.Context{
				Context: c,
				Writer:  rec,
				Request: req,
				Params:  params,
			}, false)
		})

		if err := tq.Delete(c, baseName, tsk); err != nil {
			panic(fmt.Errorf("Deleting task failed: %s", err))
		}
		ret++
	}
	return ret
}

// IterateAll iterates over all namespaces and calls Iterate on each.
func (t *Testing) IterateAll(c context.Context) int {
	total := 0
	for _, ns := range t.MustGetNamespaces(c) {
		total += t.Iterate(info.MustNamespace(c, ns))
	}
	return total
}

// FireAllTasks will force all tumble shards to run in the future.
func (t *Testing) FireAllTasks(c context.Context) {
	retryHTTP(c, func(rec *httptest.ResponseRecorder) {
		// Fire all tasks until a success or hard failure.
		t.FireAllTasksHandler(&router.Context{
			Context: c,
			Writer:  rec,
			Request: &http.Request{
				Header: http.Header{"X-Appengine-Cron": []string{"true"}},
			},
		})
	})
}

// AdvanceTime advances the test clock enough so that Iterate will be able to
// pick up tasks in the task queue.
func (t *Testing) AdvanceTime(c context.Context) {
	clk := clock.Get(c).(testclock.TestClock)
	cfg := t.GetConfig(c)
	toAdd := time.Duration(cfg.TemporalMinDelay) + time.Duration(cfg.TemporalRoundFactor) + time.Second
	logging.Infof(c, "adding %s to %s", toAdd, clk.Now().UTC())
	clk.Add(toAdd)
}

// Drain will run a loop, advancing time and iterating through tumble mutations
// until tumble's queue is empty. It returns the total number of processed
// shards.
func (t *Testing) Drain(c context.Context) int {
	ret := 0
	for {
		t.AdvanceTime(c)
		processed := t.Iterate(c)
		if processed == 0 {
			break
		}
		ret += processed
	}
	return ret
}

// DrainAll iterates over all namespaces and drains each independently.
func (t *Testing) DrainAll(c context.Context) int {
	total := 0
	for _, ns := range t.MustGetNamespaces(c) {
		total += t.Drain(info.MustNamespace(c, ns))
	}
	return total
}

// ResetLog resets the current memory logger to the empty state.
func (t *Testing) ResetLog(c context.Context) {
	logging.Get(c).(*memlogger.MemLogger).Reset()
}

// DumpLog dumps the current memory logger to stdout to help with debugging.
func (t *Testing) DumpLog(c context.Context) {
	logging.Get(c).(*memlogger.MemLogger).Dump(os.Stdout)
}

// MustGetNamespaces returns all active namespaces in t's Service.
//
// If the namespace function returns an error, MustGetNamespaces will panic.
func (t *Testing) MustGetNamespaces(c context.Context) []string {
	namespaces, err := t.getNamespaces(c, t.GetConfig(c))
	if err != nil {
		panic(err)
	}
	return namespaces
}

// retryHTTP will record an HTTP request and handle its response.
//
// It will return if the response indicated success, retry the request if the
// response indicated a transient failure, or panic if the response indicated a
// hard failure.
func retryHTTP(c context.Context, reqFn func(rec *httptest.ResponseRecorder)) {
	for {
		rec := httptest.NewRecorder()
		reqFn(rec)

		switch rec.Code {
		case http.StatusOK, http.StatusNoContent:
			return

		case http.StatusInternalServerError:
			bodyStr := rec.Body.String()
			err := fmt.Errorf("internal server error: %s", bodyStr)
			if rec.Header().Get(transientHTTPHeader) == "" {
				lmsg := logging.Get(c).(*memlogger.MemLogger).Messages()
				panic(fmt.Errorf("HTTP non-transient error: %s: %#v", err, lmsg))
			}
			logging.WithError(err).Warningf(c, "Transient error encountered, retrying.")

		default:
			panic(fmt.Errorf("HTTP error %d (%s): %s", rec.Code, http.StatusText(rec.Code), rec.Body.String()))
		}
	}
}