buckets-of-fun/lib/bucket/buckets.go

package bucket

import (
	"fmt"
	"sort"
	"strings"
)

// Buckets manages bucket objects
type Buckets []Bucket

// // action name
type actionType int

const (
	actionTypeUnknown actionType = iota
	actionTypeEmpty
	actionTypeFill
	actionTypePour
)

type action struct {
	kind   actionType
	src    int
	target int
}

type actions []action

func (a actions) String() string {
	acts := []string{}
	for _, act := range a {
		acts = append(acts, act.String())
	}
	return fmt.Sprintf("[%s]", strings.Join(acts, ","))
}

func (a action) String() string {
	switch a.kind {
	case actionTypeEmpty:
		return fmt.Sprintf("empty %d   ", a.target)
	case actionTypeFill:
		return fmt.Sprintf("fill %d    ", a.target)
	case actionTypePour:
		return fmt.Sprintf("pour %d → %d", a.src, a.target)
	case actionTypeUnknown:
	}
	return fmt.Sprintf("unknown (src: %d, target: %d)", a.src, a.target)
}

type result struct {
	mapping map[string][]actions
	matched map[string]interface{}
}

func (r *result) get(key string) ([]actions, bool) {
	acts, ok := r.mapping[key]
	return acts, ok
}

func (r *result) keys() []string {
	keys := []string{}
	for key := range r.mapping {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	return keys
}

func (r *result) matchedKeys() []string {
	keys := []string{}
	for key := range r.matched {
		keys = append(keys, key)
	}
	sort.Strings(keys)
	return keys
}

func (r *result) bestMatches() ([]string, bool) {
	var best []string
	found := false
	numActions := 0

	matched := r.matchedKeys()
	for _, key := range matched {
		acts, ok := r.get(key)
		if found == false && ok && len(acts) > 0 {
			found = true
			numActions = len(acts[0])
			best = []string{key}
			continue
		}

		if numActions > len(acts[0]) {
			numActions = len(acts[0])
			best = []string{key}
		} else if numActions == len(acts[0]) {
			best = append(best, key)
		}
	}

	if !found {
		return nil, false
	}
	return best, true
}

func (r *result) addMatch(key string) {
	r.matched[key] = struct{}{}
}

func (r *result) addActions(key string, acts actions) bool {
	currentActions, ok := r.mapping[key]
	if !ok || len(currentActions) == 0 {
		currentActions = []actions{acts}
		r.mapping[key] = currentActions
		return true
	}

	if len(acts) > len(currentActions[0]) {
		return false
	}

	if len(acts) == len(currentActions[0]) {
		r.mapping[key] = append(currentActions, acts)
		return true
	}

	r.mapping[key] = []actions{acts}
	return true
}

func (b Buckets) empty(index int) {
	buk := &b[index]
	buk.Empty()
	b[index] = *buk
}

func (b Buckets) fill(index int) {
	buk := &b[index]
	buk.Fill()
	b[index] = *buk
}

func (b Buckets) pour(i, j int) {
	src := &b[i]
	dest := &b[j]
	src.Pour(dest)
	b[i] = *src
	b[j] = *dest
}

// HasTarget returns true
func (b Buckets) HasTarget(target uint64) bool {
	for _, bucket := range b {
		if bucket.Volume == target {
			return true
		}
	}
	return false
}

func (b Buckets) String() string {
	bucketStrs := []string{}
	for _, bucket := range b {
		bucketStrs = append(bucketStrs, bucket.String())
	}
	return fmt.Sprintf("[%s]", strings.Join(bucketStrs, ","))
}

// FindTarget returns actions to find target
func (b Buckets) FindTarget(target uint64) []string {
	r := &result{
		mapping: map[string][]actions{},
		matched: map[string]interface{}{},
	}
	b.findTarget(target, r, actions{})

	keys, found := r.bestMatches()
	if !found {
		return []string{"No solution"}
	}
	fmt.Printf("%d solutions\n", len(keys))
	for i, key := range keys {
		allacts, ok := r.get(key)
		if !ok {
			continue
		}
		newState := make(Buckets, len(b))
		copy(newState, b)
		fmt.Printf("solution %d\n", i+1)
		for _, acts := range allacts {
			if len(acts) == 0 {
				fmt.Println("no actions required")
				continue
			}
			for _, act := range acts {
				newState = newState.performAction(act)
				fmt.Printf("%s\t%s\n", act.String(), newState.String())
			}
		}
	}
	ret := []string{}
	return ret
}

func (b Buckets) performAction(act action) Buckets {
	newState := make(Buckets, len(b))
	copy(newState, b)

	switch act.kind {
	case actionTypeEmpty:
		newState.empty(act.target)
	case actionTypeFill:
		newState.fill(act.target)
	case actionTypePour:
		newState.pour(act.src, act.target)
	}

	return newState
}

func (b Buckets) findTarget(
	target uint64,
	states *result,
	prevActions actions,
) {
	key := b.String()

	added := states.addActions(key, prevActions)

	if b.HasTarget(target) {
		states.addMatch(key)
		return
	}

	if !added {
		return
	}

	possibleActions := b.possibleActions()
	for _, act := range possibleActions {
		newActions := append(prevActions, act)
		newState := b.performAction(act)
		newState.findTarget(target, states, newActions)
	}
}

func (b Buckets) possibleActions() actions {
	ret := actions{}
	for i, bucket := range b {
		if !bucket.IsFull() {
			ret = append(ret, action{kind: actionTypeFill, target: i})
		}
		if !bucket.IsEmpty() {
			// ret = append(ret, action{kind: actionTypeEmpty, fn: b.empty(i), target: i})
			ret = append(ret, action{kind: actionTypeEmpty, target: i})
			for j, target := range b {
				if !target.IsFull() && i != j {
					// ret = append(ret, action{kind: actionTypePour, fn: b.pour(i, j), src: i, target: j})
					ret = append(ret, action{kind: actionTypePour, src: i, target: j})
				}
			}
		}
	}
	return ret
}