package stripe

import (
	"encoding/base64"
	"net/url"
)

// mcL applies XOR(5) to each byte, then base64 encodes, then URL encodes.
// Mirrors the MC_L function in stripe.js.
func mcL(data string) string {
	xored := make([]byte, len(data))
	for i := 0; i < len(data); i++ {
		xored[i] = data[i] ^ 5
	}
	b64 := base64.StdEncoding.EncodeToString(xored)
	return url.QueryEscape(b64)
}

// lc applies a Caesar cipher on printable ASCII (32-126) with the given shift.
// Mirrors the LC function in stripe.js.
func lc(s string, shift int) string {
	result := make([]byte, len(s))
	for i := 0; i < len(s); i++ {
		c := int(s[i])
		if c >= 32 && c <= 126 {
			result[i] = byte(((c - 32 + shift) % 95) + 32)
		} else {
			result[i] = s[i]
		}
	}
	return string(result)
}

// JsChecksum computes the js_checksum field for Stripe confirm requests.
// ppageID is the checkout session ID (cs_xxx).
// Uses dynamically fetched SV from Stripe.js.
func JsChecksum(ppageID string) string {
	sc := FetchStripeConstants()
	return mcL(ppageID + ":" + sc.SV)
}

// RvTimestamp computes the rv_timestamp field for Stripe confirm requests.
// Uses dynamically fetched RV and RVTS from Stripe.js.
func RvTimestamp() string {
	sc := FetchStripeConstants()
	return lc(sc.RV+":"+sc.RVTS, 5)
}