// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io/ioutil"
	"log"

	"fuchsia.googlesource.com/testing/catapult"
	schema "fuchsia.googlesource.com/testing/perf/schema/v1"
	"github.com/google/subcommands"
	uuid "github.com/satori/go.uuid"
)

// sharedDiagnostics contains the values to use in the HistogramSet generated
// by this subcommand.
//
// Catapult requires a specific set of shared diagnostics to be present on a
// HistogramSet before uploading to the dashboard. Those required diagnostics
// are:
//
// * bots - a GenericSet of strings containing bot hostnames
// * benchmarks - a GenericSet of strings containing Telemetry
//     benchmark names.
// * chromiumCommitPositions - a GenericSet of numbers containing
//     Chromium commit positions.
// * masters - a GenericSet of strings containing buildbot master hostnames.
//
// There are other, optional diagnostics. Those may be added to this struct as
// needed.
//
// Because the names of some diagnostics are not relevant to users of this tool
// it is ok for this subcommand and this struct to use different names for any
// of them so long as the names are mapped back to their counterparts when the
// HistogramSet is constructed.
//
// To learn more about Catapult Diagnostics, see:
// https://github.com/catapult-project/catapult/blob/master/docs/how-to-write-metrics.md
type sharedDiagnostics struct {
	// testSuite specifies the test suite that we are creating a
	// HistogramSet for. e.g. "zircon" "ledger"
	//
	// Corresponds to the diagnostic "benchmarks".
	testSuite string

	// builder specifies the LUCI builder that ran these tests.
	//
	// Corresponds to the diagnostic "bots".
	builder string

	// bucket specifies the LUCI bucket containing the job that ran
	// these tests.
	//
	// Corresponds to the diagnostic "masters".
	bucket string

	// TODO(kjharland): Add placeholder for chromiumCommitPositions
	// once the catapult team confirms what we can use this field
	// for.
}

type MakeHistogramCommand struct {
	sharedDiagnostics sharedDiagnostics
}

func (*MakeHistogramCommand) Name() string {
	return "make_histogram"
}

func (*MakeHistogramCommand) Usage() string {
	return "make_histogram [options] input_file"
}

func (*MakeHistogramCommand) Synopsis() string {
	return "Converts performance test output to a catapult HistogramSet"
}

func (cmd *MakeHistogramCommand) SetFlags(flags *flag.FlagSet) {
	flags.StringVar(&cmd.sharedDiagnostics.testSuite, "test-suite", "",
		"Test suite corresponding to the input file")
	flags.StringVar(&cmd.sharedDiagnostics.builder, "builder", "",
		"LUCI builder that generated the test results")
	flags.StringVar(&cmd.sharedDiagnostics.bucket, "bucket", "",
		"Buildbucket bucket containing the job that ran the test")
}

// Execute converts performance test output to a catapult HistogramSet
// The histogram set created by this command does not contain the necessary
// diagnostics for sending to catapult.  To add these diagnostics, use:
//
// $ catapult add_diagnostics ....
//
// See https://github.com/catapult-project/catapult/blob/master/docs/histogram-set-json-format.md
func (cmd *MakeHistogramCommand) Execute(ctx context.Context, f *flag.FlagSet, _ ...interface{}) subcommands.ExitStatus {
	if f.NArg() != 1 {
		log.Println("missing input_file")
		return subcommands.ExitFailure
	}

	inputFile := f.Arg(0)
	blob, err := ioutil.ReadFile(inputFile)
	if err != nil {
		log.Println(err)
		return subcommands.ExitFailure
	}

	histogramSet := new(catapult.HistogramSet)

	var variants struct {
		Variants []schema.Variant `json:"variants"`
	}

	if err := json.Unmarshal(blob, &variants); err != nil {
		log.Println(err)
		return subcommands.ExitFailure
	}

	// Generate Histograms from test results.
	histograms := catapult.ConvertVariantsToHistograms(variants.Variants)

	// Track whether any single Histogram addition failed. We do this instead of
	// exiting after a single error to expose as many errors as possible.
	anyAddFailed := false
	for _, histogram := range histograms {
		if err := histogramSet.AddHistogram(histogram); err != nil {
			log.Println(err)
			anyAddFailed = true
		}
	}
	if anyAddFailed {
		return subcommands.ExitFailure
	}

	// Add all shared diagnostics, mapping to the appropriate Catapult
	// diagnostic names.
	diagnosticInfoPairs := []struct {
		Name  string
		Value string
	}{
		{"benchmarks", cmd.sharedDiagnostics.testSuite},
		{"bots", cmd.sharedDiagnostics.builder},
		{"masters", cmd.sharedDiagnostics.bucket},
		// Required for uploading, even if value is just empty.
		{"chromiumCommitPositions", ""},
	}
	for _, info := range diagnosticInfoPairs {
		histogramSet.AddSharedDiagnostic(info.Name, &catapult.GenericSetDiagnostic{
			Type:   catapult.DiagnosticTypeGenericSet,
			GUID:   uuid.NewV4().String(),
			Values: []string{info.Value},
		})
	}

	// Serialize and log the new HistogramSet.
	js, err := json.Marshal(histogramSet.ToJSON())
	if err != nil {
		log.Println(err)
		return subcommands.ExitFailure
	}

	// TODO(kjharland): Add option to write to a file so this can be used
	// from a recipe.
	fmt.Println(string(js))
	return subcommands.ExitSuccess
}