// Copyright 2015 The Prometheus 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 promql

import (
	"fmt"
	"io/ioutil"
	"math"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/prometheus/common/model"

	"github.com/prometheus/prometheus/storage"
	"github.com/prometheus/prometheus/storage/local"
	"github.com/prometheus/prometheus/util/strutil"
	"github.com/prometheus/prometheus/util/testutil"
)

var (
	minNormal = math.Float64frombits(0x0010000000000000) // The smallest positive normal value of type float64.

	patSpace       = regexp.MustCompile("[\t ]+")
	patLoad        = regexp.MustCompile(`^load\s+(.+?)$`)
	patEvalInstant = regexp.MustCompile(`^eval(?:_(fail|ordered))?\s+instant\s+(?:at\s+(.+?))?\s+(.+)$`)
)

const (
	testStartTime = model.Time(0)
	epsilon       = 0.000001 // Relative error allowed for sample values.
	maxErrorCount = 10
)

// Test is a sequence of read and write commands that are run
// against a test storage.
type Test struct {
	testutil.T

	cmds []testCommand

	storage      local.Storage
	closeStorage func()
	queryEngine  *Engine
}

// NewTest returns an initialized empty Test.
func NewTest(t testutil.T, input string) (*Test, error) {
	test := &Test{
		T:    t,
		cmds: []testCommand{},
	}
	err := test.parse(input)
	test.clear()

	return test, err
}

func NewTestFromFile(t testutil.T, filename string) (*Test, error) {
	content, err := ioutil.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	return NewTest(t, string(content))
}

// QueryEngine returns the test's query engine.
func (t *Test) QueryEngine() *Engine {
	return t.queryEngine
}

// Storage returns the test's storage.
func (t *Test) Storage() local.Storage {
	return t.storage
}

func raise(line int, format string, v ...interface{}) error {
	return &ParseErr{
		Line: line + 1,
		Err:  fmt.Errorf(format, v...),
	}
}

func (t *Test) parseLoad(lines []string, i int) (int, *loadCmd, error) {
	if !patLoad.MatchString(lines[i]) {
		return i, nil, raise(i, "invalid load command. (load <step:duration>)")
	}
	parts := patLoad.FindStringSubmatch(lines[i])

	gap, err := strutil.StringToDuration(parts[1])
	if err != nil {
		return i, nil, raise(i, "invalid step definition %q: %s", parts[1], err)
	}
	cmd := newLoadCmd(gap)
	for i+1 < len(lines) {
		i++
		defLine := lines[i]
		if len(defLine) == 0 {
			i--
			break
		}
		metric, vals, err := parseSeriesDesc(defLine)
		if err != nil {
			if perr, ok := err.(*ParseErr); ok {
				perr.Line = i + 1
			}
			return i, nil, err
		}
		cmd.set(metric, vals...)
	}
	return i, cmd, nil
}

func (t *Test) parseEval(lines []string, i int) (int, *evalCmd, error) {
	if !patEvalInstant.MatchString(lines[i]) {
		return i, nil, raise(i, "invalid evaluation command. (eval[_fail|_ordered] instant [at <offset:duration>] <query>")
	}
	parts := patEvalInstant.FindStringSubmatch(lines[i])
	var (
		mod = parts[1]
		at  = parts[2]
		qry = parts[3]
	)
	expr, err := ParseExpr(qry)
	if err != nil {
		if perr, ok := err.(*ParseErr); ok {
			perr.Line = i + 1
			perr.Pos += strings.Index(lines[i], qry)
		}
		return i, nil, err
	}

	offset, err := strutil.StringToDuration(at)
	if err != nil {
		return i, nil, raise(i, "invalid step definition %q: %s", parts[1], err)
	}
	ts := testStartTime.Add(offset)

	cmd := newEvalCmd(expr, ts, ts, 0)
	switch mod {
	case "ordered":
		cmd.ordered = true
	case "fail":
		cmd.fail = true
	}

	for j := 1; i+1 < len(lines); j++ {
		i++
		defLine := lines[i]
		if len(defLine) == 0 {
			i--
			break
		}
		if f, err := parseNumber(defLine); err == nil {
			cmd.expect(0, nil, sequenceValue{value: model.SampleValue(f)})
			break
		}
		metric, vals, err := parseSeriesDesc(defLine)
		if err != nil {
			if perr, ok := err.(*ParseErr); ok {
				perr.Line = i + 1
			}
			return i, nil, err
		}

		// Currently, we are not expecting any matrices.
		if len(vals) > 1 {
			return i, nil, raise(i, "expecting multiple values in instant evaluation not allowed")
		}
		cmd.expect(j, metric, vals...)
	}
	return i, cmd, nil
}

// parse the given command sequence and appends it to the test.
func (t *Test) parse(input string) error {
	// Trim lines and remove comments.
	lines := strings.Split(input, "\n")
	for i, l := range lines {
		l = strings.TrimSpace(l)
		if strings.HasPrefix(l, "#") {
			l = ""
		}
		lines[i] = l
	}
	var err error

	// Scan for steps line by line.
	for i := 0; i < len(lines); i++ {
		l := lines[i]
		if len(l) == 0 {
			continue
		}
		var cmd testCommand

		switch c := strings.ToLower(patSpace.Split(l, 2)[0]); {
		case c == "clear":
			cmd = &clearCmd{}
		case c == "load":
			i, cmd, err = t.parseLoad(lines, i)
		case strings.HasPrefix(c, "eval"):
			i, cmd, err = t.parseEval(lines, i)
		default:
			return raise(i, "invalid command %q", l)
		}
		if err != nil {
			return err
		}
		t.cmds = append(t.cmds, cmd)
	}
	return nil
}

// testCommand is an interface that ensures that only the package internal
// types can be a valid command for a test.
type testCommand interface {
	testCmd()
}

func (*clearCmd) testCmd() {}
func (*loadCmd) testCmd()  {}
func (*evalCmd) testCmd()  {}

// loadCmd is a command that loads sequences of sample values for specific
// metrics into the storage.
type loadCmd struct {
	gap     time.Duration
	metrics map[model.Fingerprint]model.Metric
	defs    map[model.Fingerprint][]model.SamplePair
}

func newLoadCmd(gap time.Duration) *loadCmd {
	return &loadCmd{
		gap:     gap,
		metrics: map[model.Fingerprint]model.Metric{},
		defs:    map[model.Fingerprint][]model.SamplePair{},
	}
}

func (cmd loadCmd) String() string {
	return "load"
}

// set a sequence of sample values for the given metric.
func (cmd *loadCmd) set(m model.Metric, vals ...sequenceValue) {
	fp := m.Fingerprint()

	samples := make([]model.SamplePair, 0, len(vals))
	ts := testStartTime
	for _, v := range vals {
		if !v.omitted {
			samples = append(samples, model.SamplePair{
				Timestamp: ts,
				Value:     v.value,
			})
		}
		ts = ts.Add(cmd.gap)
	}
	cmd.defs[fp] = samples
	cmd.metrics[fp] = m
}

// append the defined time series to the storage.
func (cmd *loadCmd) append(a storage.SampleAppender) {
	for fp, samples := range cmd.defs {
		met := cmd.metrics[fp]
		for _, smpl := range samples {
			s := &model.Sample{
				Metric:    met,
				Value:     smpl.Value,
				Timestamp: smpl.Timestamp,
			}
			a.Append(s)
		}
	}
}

// evalCmd is a command that evaluates an expression for the given time (range)
// and expects a specific result.
type evalCmd struct {
	expr       Expr
	start, end model.Time
	interval   time.Duration

	instant       bool
	fail, ordered bool

	metrics  map[model.Fingerprint]model.Metric
	expected map[model.Fingerprint]entry
}

type entry struct {
	pos  int
	vals []sequenceValue
}

func (e entry) String() string {
	return fmt.Sprintf("%d: %s", e.pos, e.vals)
}

func newEvalCmd(expr Expr, start, end model.Time, interval time.Duration) *evalCmd {
	return &evalCmd{
		expr:     expr,
		start:    start,
		end:      end,
		interval: interval,
		instant:  start == end && interval == 0,

		metrics:  map[model.Fingerprint]model.Metric{},
		expected: map[model.Fingerprint]entry{},
	}
}

func (ev *evalCmd) String() string {
	return "eval"
}

// expect adds a new metric with a sequence of values to the set of expected
// results for the query.
func (ev *evalCmd) expect(pos int, m model.Metric, vals ...sequenceValue) {
	if m == nil {
		ev.expected[0] = entry{pos: pos, vals: vals}
		return
	}
	fp := m.Fingerprint()
	ev.metrics[fp] = m
	ev.expected[fp] = entry{pos: pos, vals: vals}
}

// compareResult compares the result value with the defined expectation.
func (ev *evalCmd) compareResult(result Value) error {
	switch val := result.(type) {
	case Matrix:
		if ev.instant {
			return fmt.Errorf("received range result on instant evaluation")
		}
		seen := map[model.Fingerprint]bool{}
		for pos, v := range val {
			fp := v.Metric.Metric.Fingerprint()
			if _, ok := ev.metrics[fp]; !ok {
				return fmt.Errorf("unexpected metric %s in result", v.Metric.Metric)
			}
			exp := ev.expected[fp]
			if ev.ordered && exp.pos != pos+1 {
				return fmt.Errorf("expected metric %s with %v at position %d but was at %d", v.Metric.Metric, exp.vals, exp.pos, pos+1)
			}
			for i, expVal := range exp.vals {
				if !almostEqual(float64(expVal.value), float64(v.Values[i].Value)) {
					return fmt.Errorf("expected %v for %s but got %v", expVal, v.Metric.Metric, v.Values)
				}
			}
			seen[fp] = true
		}
		for fp, expVals := range ev.expected {
			if !seen[fp] {
				return fmt.Errorf("expected metric %s with %v not found", ev.metrics[fp], expVals)
			}
		}

	case Vector:
		if !ev.instant {
			fmt.Errorf("received instant result on range evaluation")
		}
		seen := map[model.Fingerprint]bool{}
		for pos, v := range val {
			fp := v.Metric.Metric.Fingerprint()
			if _, ok := ev.metrics[fp]; !ok {
				return fmt.Errorf("unexpected metric %s in result", v.Metric.Metric)
			}
			exp := ev.expected[fp]
			if ev.ordered && exp.pos != pos+1 {
				return fmt.Errorf("expected metric %s with %v at position %d but was at %d", v.Metric.Metric, exp.vals, exp.pos, pos+1)
			}
			if !almostEqual(float64(exp.vals[0].value), float64(v.Value)) {
				return fmt.Errorf("expected %v for %s but got %v", exp.vals[0].value, v.Metric.Metric, v.Value)
			}

			seen[fp] = true
		}
		for fp, expVals := range ev.expected {
			if !seen[fp] {
				return fmt.Errorf("expected metric %s with %v not found", ev.metrics[fp], expVals)
			}
		}

	case *Scalar:
		if !almostEqual(float64(ev.expected[0].vals[0].value), float64(val.Value)) {
			return fmt.Errorf("expected scalar %v but got %v", val.Value, ev.expected[0].vals[0].value)
		}

	default:
		panic(fmt.Errorf("promql.Test.compareResult: unexpected result type %T", result))
	}
	return nil
}

// clearCmd is a command that wipes the test's storage state.
type clearCmd struct{}

func (cmd clearCmd) String() string {
	return "clear"
}

// Run executes the command sequence of the test. Until the maximum error number
// is reached, evaluation errors do not terminate execution.
func (t *Test) Run() error {
	for _, cmd := range t.cmds {
		err := t.exec(cmd)
		// TODO(fabxc): aggregate command errors, yield diffs for result
		// comparison errors.
		if err != nil {
			return err
		}
	}
	return nil
}

// exec processes a single step of the test
func (t *Test) exec(tc testCommand) error {
	switch cmd := tc.(type) {
	case *clearCmd:
		t.clear()

	case *loadCmd:
		cmd.append(t.storage)
		t.storage.WaitForIndexing()

	case *evalCmd:
		q := t.queryEngine.newQuery(cmd.expr, cmd.start, cmd.end, cmd.interval)
		res := q.Exec()
		if res.Err != nil {
			if cmd.fail {
				return nil
			}
			return fmt.Errorf("error evaluating query: %s", res.Err)
		}
		if res.Err == nil && cmd.fail {
			return fmt.Errorf("expected error evaluating query but got none")
		}

		err := cmd.compareResult(res.Value)
		if err != nil {
			return fmt.Errorf("error in %s %s: %s", cmd, cmd.expr, err)
		}

	default:
		panic("promql.Test.exec: unknown test command type")
	}
	return nil
}

// clear the current test storage of all inserted samples.
func (t *Test) clear() {
	if t.closeStorage != nil {
		t.closeStorage()
	}
	if t.queryEngine != nil {
		t.queryEngine.Stop()
	}

	var closer testutil.Closer
	t.storage, closer = local.NewTestStorage(t, 1)

	t.closeStorage = closer.Close
	t.queryEngine = NewEngine(t.storage, nil)
}

func (t *Test) Close() {
	t.queryEngine.Stop()
	t.closeStorage()
}

// samplesAlmostEqual returns true if the two sample lines only differ by a
// small relative error in their sample value.
func almostEqual(a, b float64) bool {
	// NaN has no equality but for testing we still want to know whether both values
	// are NaN.
	if math.IsNaN(a) && math.IsNaN(b) {
		return true
	}

	// Cf. http://floating-point-gui.de/errors/comparison/
	if a == b {
		return true
	}

	diff := math.Abs(a - b)

	if a == 0 || b == 0 || diff < minNormal {
		return diff < epsilon*minNormal
	}
	return diff/(math.Abs(a)+math.Abs(b)) < epsilon
}

func parseNumber(s string) (float64, error) {
	n, err := strconv.ParseInt(s, 0, 64)
	f := float64(n)
	if err != nil {
		f, err = strconv.ParseFloat(s, 64)
	}
	if err != nil {
		return 0, fmt.Errorf("error parsing number: %s", err)
	}
	return f, nil
}