// Package economy contains helpers for computing and formatting token rewards.
package economy

import (
	"fmt"

	"go-blockchain/blockchain"
)

// BlockFeeBreakdown describes the fee income for a committed block validator.
// There is no minting — validators earn only the fees paid by transactions.
type BlockFeeBreakdown struct {
	ValidatorPubKey string
	BlockIndex      uint64
	TxFees          uint64 // sum of all transaction fees in the block
	IsGenesis       bool   // true for block 0 (genesis allocation, not fees)
	GenesisAmount   uint64
}

// ComputeBlockReward calculates the fee income for a committed block.
func ComputeBlockReward(b *blockchain.Block) BlockFeeBreakdown {
	d := BlockFeeBreakdown{
		ValidatorPubKey: b.Validator,
		BlockIndex:      b.Index,
		TxFees:          b.TotalFees,
	}
	if b.Index == 0 {
		d.IsGenesis = true
		d.GenesisAmount = blockchain.GenesisAllocation
	}
	return d
}

// Total returns how much the validator actually receives for this block.
func (d BlockFeeBreakdown) Total() uint64 {
	if d.IsGenesis {
		return d.GenesisAmount
	}
	return d.TxFees
}

// Summary prints a human-readable reward summary.
func (d BlockFeeBreakdown) Summary() string {
	if d.IsGenesis {
		return fmt.Sprintf(
			"Block #0 (genesis): validator %s...%s receives genesis allocation %s",
			d.ValidatorPubKey[:8], d.ValidatorPubKey[len(d.ValidatorPubKey)-4:],
			FormatTokens(d.GenesisAmount),
		)
	}
	if d.TxFees == 0 {
		return fmt.Sprintf(
			"Block #%d committed: validator %s...%s — no fees",
			d.BlockIndex,
			d.ValidatorPubKey[:8], d.ValidatorPubKey[len(d.ValidatorPubKey)-4:],
		)
	}
	return fmt.Sprintf(
		"Block #%d committed: validator %s...%s earns %s in fees",
		d.BlockIndex,
		d.ValidatorPubKey[:8], d.ValidatorPubKey[len(d.ValidatorPubKey)-4:],
		FormatTokens(d.TxFees),
	)
}

// FormatTokens converts micro-tokens to a human-readable string.
func FormatTokens(microTokens uint64) string {
	whole := microTokens / blockchain.Token
	frac := microTokens % blockchain.Token
	return fmt.Sprintf("%d.%06d T", whole, frac)
}