package game

import (
	"errors"
	"regexp"
	"strconv"
)

type effect interface {
	apply(*LocalState)
	end(*LocalState)
}

type dynamicEffect struct {
	_apply func(*LocalState)
	_end   func(*LocalState)
}

func (e *dynamicEffect) apply(s *LocalState) {
	e._apply(s)
}

func (e *dynamicEffect) end(s *LocalState) {
	e._end(s)
}

func newCombinedEffect(effects []effect) *dynamicEffect {
	return &dynamicEffect{
		_apply: func(s *LocalState) {
			for _, e := range effects {
				e.apply(s)
			}
		},
		_end: func(s *LocalState) {
			for _, e := range effects {
				e.end(s)
			}
		},
	}
}

func newAdjustmentEffect(adjust func(Permanent, int), u *Unit, delta int) effect {
	apply := func(*LocalState) { adjust(u, delta) }
	end := func(*LocalState) { adjust(u, -delta) }
	return &dynamicEffect{apply, end}
}

func newMeleeModificationEffect(u *Unit, delta int) effect {
	return newAdjustmentEffect(adjustMelee, u, delta)
}

func newAttackModificationEffect(u *Unit, delta int) effect {
	return newAdjustmentEffect(adjustAttack, u, delta)
}

func newMovementModificationEffect(u *Unit, delta int) effect {
	return newAdjustmentEffect(adjustMovement, u, delta)
}

func newHealthModificationEffect(u *Unit, delta int) effect {
	return newAdjustmentEffect(adjustHealth, u, delta)
}

func newTmpEffect(p Permanent, effect string) effect {
	apply := func(*LocalState) { p.addTmpEffect(effect) }
	end := func(*LocalState) { p.removeTmpEffect(effect) }
	return &dynamicEffect{apply, end}
}

type xEffect struct {
	// amount of the effect
	x int
	// does the effect set or adjust the value
	set bool
	// raw effect description
	raw string
}

type ErrXEffectError struct {
	err error
}

func (e ErrXEffectError) Error() string {
	return e.err.Error()
}

var ErrXEffectFormat = ErrXEffectError{errors.New("invalid format")}

var (
	xEffectXSuffix = regexp.MustCompile(`^\S+ ([\+-]?)(\d+)`)
	xEffectXPrefix = regexp.MustCompile(`^([\+-]?)(\d+) \S+`)
)

func parseXEffect(desc string) (e xEffect, err error) {
	if freeActionRegex.FindString(desc) != "" {
		return e, ErrXEffectFormat
	}

	e.raw = desc
	m := xEffectXSuffix.FindAllStringSubmatch(desc, -1)
	if len(m) == 0 {
		m = xEffectXPrefix.FindAllStringSubmatch(desc, -1)
	}

	if len(m) != 0 {
		e.set = m[0][1] == ""

		e.x, err = strconv.Atoi(m[0][1] + m[0][2])
		if err != nil {
			return e, ErrXEffectError{err}
		}
		return e, nil
	}

	// Both regex did not match
	return e, ErrXEffectFormat
}