/*
Copyright (c) 2016-2017 VMware, Inc. All Rights Reserved.

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 object

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"reflect"
	"strings"
	"text/tabwriter"

	"github.com/vmware/govmomi/govc/cli"
	"github.com/vmware/govmomi/govc/flags"
	"github.com/vmware/govmomi/property"
	"github.com/vmware/govmomi/view"
	"github.com/vmware/govmomi/vim25/methods"
	"github.com/vmware/govmomi/vim25/types"
)

type collect struct {
	*flags.DatacenterFlag

	single bool
	simple bool
	n      int
	kind   kinds

	filter property.Filter
	obj    string
}

func init() {
	cli.Register("object.collect", &collect{})
}

func (cmd *collect) Register(ctx context.Context, f *flag.FlagSet) {
	cmd.DatacenterFlag, ctx = flags.NewDatacenterFlag(ctx)
	cmd.DatacenterFlag.Register(ctx, f)

	f.BoolVar(&cmd.simple, "s", false, "Output property value only")
	f.IntVar(&cmd.n, "n", 0, "Wait for N property updates")
	f.Var(&cmd.kind, "type", "Resource type.  If specified, MOID is used for a container view root")
}

func (cmd *collect) Usage() string {
	return "[MOID] [PROPERTY]..."
}

func (cmd *collect) Description() string {
	return `Collect managed object properties.

MOID can be an inventory path or ManagedObjectReference.
MOID defaults to '-', an alias for 'ServiceInstance:ServiceInstance' or the root folder if a '-type' flag is given.

If a '-type' flag is given, properties are collected using a ContainerView object where MOID is the root of the view.

By default only the current property value(s) are collected.  To wait for updates, use the '-n' flag or
specify a property filter.  A property filter can be specified by prefixing the property name with a '-',
followed by the value to match.

Examples:
  govc object.collect - content
  govc object.collect -s HostSystem:ha-host hardware.systemInfo.uuid
  govc object.collect -s /ha-datacenter/vm/foo overallStatus
  govc object.collect -s /ha-datacenter/vm/foo -guest.guestOperationsReady true # property filter
  govc object.collect -type m / name runtime.powerState # collect properties for multiple objects
  govc object.collect -json -n=-1 EventManager:ha-eventmgr latestEvent | jq .
  govc object.collect -json -s $(govc object.collect -s - content.perfManager) description.counterType | jq .`
}

func (cmd *collect) Process(ctx context.Context) error {
	if err := cmd.DatacenterFlag.Process(ctx); err != nil {
		return err
	}
	return nil
}

var stringer = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()

type change struct {
	cmd    *collect
	Update types.ObjectUpdate
}

func (pc *change) MarshalJSON() ([]byte, error) {
	if len(pc.cmd.kind) == 0 {
		return json.Marshal(pc.Update.ChangeSet)
	}

	return json.Marshal(pc.Update)
}

func (pc *change) output(name string, rval reflect.Value, rtype reflect.Type) {
	s := "..."

	kind := rval.Kind()

	if kind == reflect.Ptr || kind == reflect.Interface {
		if rval.IsNil() {
			s = ""
		} else {
			rval = rval.Elem()
			kind = rval.Kind()
		}
	}

	switch kind {
	case reflect.Ptr, reflect.Interface:
	case reflect.Slice:
		if rval.Len() == 0 {
			s = ""
			break
		}

		etype := rtype.Elem()

		if etype.Kind() != reflect.Interface && etype.Kind() != reflect.Struct || etype.Implements(stringer) {
			var val []string

			for i := 0; i < rval.Len(); i++ {
				v := rval.Index(i).Interface()

				if fstr, ok := v.(fmt.Stringer); ok {
					s = fstr.String()
				} else {
					s = fmt.Sprintf("%v", v)
				}

				val = append(val, s)
			}

			s = strings.Join(val, ",")
		}
	case reflect.Struct:
		if rtype.Implements(stringer) {
			s = rval.Interface().(fmt.Stringer).String()
		}
	default:
		s = fmt.Sprintf("%v", rval.Interface())
	}

	if pc.cmd.simple {
		fmt.Fprintln(pc.cmd.Out, s)
		return
	}

	if pc.cmd.obj != "" {
		fmt.Fprintf(pc.cmd.Out, "%s\t", pc.cmd.obj)
	}

	fmt.Fprintf(pc.cmd.Out, "%s\t%s\t%s\n", name, rtype, s)
}

func (pc *change) writeStruct(name string, rval reflect.Value, rtype reflect.Type) {
	for i := 0; i < rval.NumField(); i++ {
		fval := rval.Field(i)
		field := rtype.Field(i)

		if field.Anonymous {
			pc.writeStruct(name, fval, fval.Type())
			continue
		}

		fname := fmt.Sprintf("%s.%s%s", name, strings.ToLower(field.Name[:1]), field.Name[1:])
		pc.output(fname, fval, field.Type)
	}
}

func (pc *change) Write(w io.Writer) error {
	tw := tabwriter.NewWriter(pc.cmd.Out, 4, 0, 2, ' ', 0)
	pc.cmd.Out = tw

	for _, c := range pc.Update.ChangeSet {
		if c.Val == nil {
			// type is unknown in this case, as xsi:type was not provided - just skip for now
			continue
		}

		rval := reflect.ValueOf(c.Val)
		rtype := rval.Type()

		if strings.HasPrefix(rtype.Name(), "ArrayOf") {
			rval = rval.Field(0)
			rtype = rval.Type()
		}

		if len(pc.cmd.kind) != 0 {
			pc.cmd.obj = pc.Update.Obj.String()
		}

		if pc.cmd.single && rtype.Kind() == reflect.Struct && !rtype.Implements(stringer) {
			pc.writeStruct(c.Name, rval, rtype)
			continue
		}

		pc.output(c.Name, rval, rtype)
	}

	return tw.Flush()
}

func (cmd *collect) match(update types.ObjectUpdate) bool {
	if len(cmd.filter) == 0 {
		return false
	}

	for _, c := range update.ChangeSet {
		if cmd.filter.MatchProperty(types.DynamicProperty{Name: c.Name, Val: c.Val}) {
			return true
		}
	}

	return false
}

func (cmd *collect) toFilter(f *flag.FlagSet, props []string) ([]string, error) {
	// TODO: Only supporting 1 filter prop for now.  More than one would require some
	// accounting / accumulating of multiple updates.  And need to consider objects
	// then enter/leave a container view.
	if len(props) != 2 || !strings.HasPrefix(props[0], "-") {
		return props, nil
	}

	cmd.filter = property.Filter{props[0][1:]: props[1]}

	return cmd.filter.Keys(), nil
}

func (cmd *collect) Run(ctx context.Context, f *flag.FlagSet) error {
	client, err := cmd.Client()
	if err != nil {
		return err
	}

	finder, err := cmd.Finder()
	if err != nil {
		return err
	}

	ref := methods.ServiceInstance
	arg := f.Arg(0)

	if len(cmd.kind) != 0 {
		ref = client.ServiceContent.RootFolder
	}

	switch arg {
	case "", "-":
	default:
		if !ref.FromString(arg) {
			l, ferr := finder.ManagedObjectList(ctx, arg)
			if ferr != nil {
				return err
			}

			switch len(l) {
			case 0:
				return fmt.Errorf("%s not found", arg)
			case 1:
				ref = l[0].Object.Reference()
			default:
				return flag.ErrHelp
			}
		}
	}

	p := property.DefaultCollector(client)
	filter := new(property.WaitFilter)

	var props []string
	if f.NArg() > 1 {
		props = f.Args()[1:]
		cmd.single = len(props) == 1
	}

	props, err = cmd.toFilter(f, props)
	if err != nil {
		return err
	}

	if len(cmd.kind) == 0 {
		filter.Add(ref, ref.Type, props)
	} else {
		m := view.NewManager(client)

		v, err := m.CreateContainerView(ctx, ref, cmd.kind, true)
		if err != nil {
			return err
		}

		defer v.Destroy(ctx)

		for _, kind := range cmd.kind {
			filter.Add(v.Reference(), kind, props, v.TraversalSpec())
		}
	}

	entered := false
	hasFilter := len(cmd.filter) != 0

	return property.WaitForUpdates(ctx, p, filter, func(updates []types.ObjectUpdate) bool {
		matches := 0

		for _, update := range updates {
			if entered && update.Kind == types.ObjectUpdateKindEnter {
				// on the first update we only get kind "enter"
				// if a new object is added, the next update with have both "enter" and "modify".
				continue
			}

			c := &change{cmd, update}

			if hasFilter {
				if cmd.match(update) {
					matches++
				} else {
					continue
				}
			}

			_ = cmd.WriteResult(c)
		}

		entered = true

		if hasFilter {
			if matches > 0 {
				return true
			}

			return false
		}

		cmd.n--

		return cmd.n == -1
	})
}
