package common

import "fmt"

// The action processor applies each crossed level's properties, capacity and
// shop weights together with this plan. It must not credit an EXP purchase
// separately from its gold/HP debit or persist only part of the level effects.
type CurrencyWarsExperiencePlan struct {
	Level   uint32
	Exp     uint32
	Crossed []CurrencyWarsPlayerLevel
}

// PlanBaseExperience uses the captured thresholds before run modifiers.
// levelLimit is the resolved run limit, not a fallback to a normal-mode cap.
// Residual EXP at that limit is retained in the returned plan; callers must
// apply a separately established cap/reset policy before encoding the Client
// counter. This function does not guess that policy or spend any currency.
func (c *CurrencyWarsCatalog) PlanBaseExperience(level, exp, gain, levelLimit uint32) (CurrencyWarsExperiencePlan, error) {
	var empty CurrencyWarsExperiencePlan
	if c == nil || level == 0 || levelLimit < level {
		return empty, fmt.Errorf("CW experience level/limit is invalid")
	}
	if _, err := c.PlayerLevel(levelLimit); err != nil {
		return empty, fmt.Errorf("CW experience limit: %w", err)
	}
	current, err := c.PlayerLevel(level)
	if err != nil {
		return empty, err
	}
	if level < levelLimit && (current.LevelUpExp == 0 || exp >= current.LevelUpExp) {
		return empty, fmt.Errorf("CW initial experience counter is not normalized")
	}
	plan := CurrencyWarsExperiencePlan{Level: level}
	remaining := uint64(exp) + uint64(gain)
	for plan.Level < levelLimit {
		if current.LevelUpExp == 0 {
			return empty, fmt.Errorf("CW level %d has no positive EXP threshold", plan.Level)
		}
		if remaining < uint64(current.LevelUpExp) {
			break
		}
		remaining -= uint64(current.LevelUpExp)
		plan.Level++
		current, err = c.PlayerLevel(plan.Level)
		if err != nil {
			return empty, err
		}
		plan.Crossed = append(plan.Crossed, current)
	}
	if remaining > uint64(^uint32(0)) {
		return empty, fmt.Errorf("CW experience counter overflows protocol uint32")
	}
	plan.Exp = uint32(remaining)
	return plan, nil
}