package v1

import (
	"errors"
	"strconv"

	u256 "gno.land/p/gnoswap/uint256"
	ufmt "gno.land/p/nt/ufmt/v0"
)

var one = u256.One()

// ErrorMessages define all error message templates used throughout the router
const (
	// slippage validation
	errExactOutAmountExceeded = "received more than requested in requested=%d, actual=%d"

	// route validation
	errInvalidRouteLength = "route length(%d) must be 1~7"

	// quote validation
	errRoutesQuotesMismatch = "mismatch between routes(%d) and quotes(%d) length"
	errInvalidQuote         = "invalid quote(%s) at index(%d)"
	errInvalidQuoteValue    = "quote(%s) at index(%d) must be positive value"
	errQuoteExceedsMax      = "quote(%s) at index(%d) must be less than or equal to %d"
	errQuoteSumExceedsMax   = "quote sum exceeds 100 at index(%d)"
	errInvalidQuoteSum      = "quote sum(%d) must be 100"

	// swap type validation
	errExactInTooFewReceived = "ExactIn: too few received (min:%d, got:%d)"
	errExactOutTooMuchSpent  = "ExactOut: too much spent (max:%d, used:%d)"

	// route parsing validation
	errEmptyRoutes = "routes cannot be empty"
)

// SwapValidator provides validation methods for swap operations
type SwapValidator struct{}

// exactOutAmount checks if output amount meets specified requirements.
// For exact-out swaps, the output must be exactly the specified amount with tolerance up to swapCount units for rounding.
func (v *SwapValidator) exactOutAmount(resultAmount, specifiedAmount int64, swapCount int64) error {
	diff := int64(0)

	if resultAmount >= specifiedAmount {
		diff = resultAmount - specifiedAmount
	} else {
		diff = specifiedAmount - resultAmount
	}

	if diff > swapCount {
		return ufmt.Errorf(errExactOutAmountExceeded, specifiedAmount, resultAmount)
	}

	return nil
}

// slippage ensures swap amounts meet slippage requirements.
func (v *SwapValidator) slippage(swapType SwapType, amountIn, amountOut, limit int64) error {
	switch swapType {
	case ExactIn:
		if amountOut < limit {
			return ufmt.Errorf(errExactInTooFewReceived, limit, amountOut)
		}
	case ExactOut:
		if amountIn > limit {
			return ufmt.Errorf(errExactOutTooMuchSpent, limit, amountIn)
		}
	default:
		return errInvalidSwapType
	}
	return nil
}

// swapType ensures the swap type string is valid.
func (v *SwapValidator) swapType(swapTypeStr string) (SwapType, error) {
	swapType, err := trySwapTypeFromStr(swapTypeStr)
	if err != nil {
		return Unknown, errInvalidSwapType
	}
	return swapType, nil
}

// amount ensures the amount is properly formatted and positive.
func (v *SwapValidator) amount(amount int64) (int64, error) {
	if amount <= 0 {
		return 0, ufmt.Errorf(ErrInvalidPositiveAmount, amount)
	}
	return amount, nil
}

// amountLimit ensures the amount limit is properly formatted and non-zero.
func (v *SwapValidator) amountLimit(amountLimit int64) (int64, error) {
	if amountLimit <= 0 {
		return 0, ufmt.Errorf(ErrInvalidZeroAmountLimit, amountLimit)
	}
	return amountLimit, nil
}

// RouteParser handles parsing and validation of routes and quotes
type RouteParser struct{}

// NewRouteParser creates a new route parser instance.
func NewRouteParser() *RouteParser {
	return &RouteParser{}
}

// ParseRoutes parses route and quote strings into slices and validates them.
func (p *RouteParser) ParseRoutes(routes, quotes string) ([]string, []string, error) {
	// Check for empty routes
	if routes == "" || quotes == "" {
		return nil, nil, errors.New(errEmptyRoutes)
	}

	routesArr := splitSingleChar(routes, ',')
	quotesArr := splitSingleChar(quotes, ',')

	if err := p.ValidateRoutesAndQuotes(routesArr, quotesArr); err != nil {
		return nil, nil, err
	}

	return routesArr, quotesArr, nil
}

// ValidateRoutesAndQuotes ensures routes and quotes meet required criteria.
func (p *RouteParser) ValidateRoutesAndQuotes(routes, quotes []string) error {
	rr := len(routes)
	qq := len(quotes)

	if rr < 1 || rr > 7 {
		return ufmt.Errorf(errInvalidRouteLength, rr)
	}

	if rr != qq {
		return ufmt.Errorf(errRoutesQuotesMismatch, rr, qq)
	}

	return p.ValidateQuoteSum(quotes)
}

// ValidateQuoteSum ensures all quotes add up to 100%.
func (p *RouteParser) ValidateQuoteSum(quotes []string) error {
	const (
		maxQuote int8 = 100
		minQuote int8 = 0
	)

	var sum int8

	for i, quote := range quotes {
		qt, err := strconv.ParseInt(quote, 10, 8)
		if err != nil {
			return ufmt.Errorf(errInvalidQuote, quote, i)
		}
		intQuote := int8(qt)

		// Quote must be positive (> 0) as each route needs a non-zero allocation.
		// A quote of 0 would mean no swap through that route, which is invalid.
		if intQuote <= minQuote { // minQuote = 0, so this rejects quote = 0
			return ufmt.Errorf(errInvalidQuoteValue, quote, i)
		}

		if intQuote > maxQuote {
			return ufmt.Errorf(errQuoteExceedsMax, quote, i, maxQuote)
		}

		if sum > maxQuote-intQuote {
			return ufmt.Errorf(errQuoteSumExceedsMax, i)
		}

		sum += intQuote
	}

	if sum != maxQuote {
		return ufmt.Errorf(errInvalidQuoteSum, sum)
	}

	return nil
}

// finalizeSwap handles post-swap operations and validations.
func (r *routerV1) finalizeSwap(
	_ int,
	rlm realm,
	inputToken, outputToken string,
	resultAmountIn, resultAmountOut int64,
	swapType SwapType,
	tokenAmountLimit int64,
	amountSpecified int64,
	swapCount int64,
	isSetSqrtPriceLimitX96 bool,
) (int64, int64) {
	validator := &SwapValidator{}

	// Handle swap fee
	resultAmountOutWithoutFee := r.handleSwapFee(0, rlm, outputToken, resultAmountOut)

	// Validate exact out amount if applicable
	// If sqrtPriceLimitX96 is set, slippage check is not needed
	if swapType == ExactOut && !isSetSqrtPriceLimitX96 {
		if err := validator.exactOutAmount(resultAmountOutWithoutFee, amountSpecified, swapCount); err != nil {
			panic(addDetailToError(errSlippage, err.Error()))
		}
	}

	if err := validator.slippage(swapType, resultAmountIn, resultAmountOutWithoutFee, tokenAmountLimit); err != nil {
		panic(addDetailToError(errSlippage, err.Error()))
	}

	return resultAmountIn, resultAmountOutWithoutFee
}

// validateRoutesAndQuotes is a convenience function that parses and validates routes in one call.
func validateRoutesAndQuotes(routes, quotes string) ([]string, []string, error) {
	return NewRouteParser().ParseRoutes(routes, quotes)
}