package client

import (
	"net/url"
	"strconv"
	"strings"
)

// InterchainOption configures an interchain-trace request (Transaction.GetInterchain
// / Block.GetInterchain). Anchor proofs are chained, so by default the trace
// returns the first anchor per public chain; these options change how many and
// which chains are returned.
type InterchainOption func(*interchainConfig)

type interchainConfig struct {
	perChain *int
	chains   []string
}

// WithPerChain caps how many interchain anchors are returned per public chain,
// earliest-first: 1 is the first anchor per chain (the service default), 0
// returns all anchors for each chain.
func WithPerChain(n int) InterchainOption {
	return func(c *interchainConfig) { c.perChain = &n }
}

// WithChains restricts the trace to these interchain chain ids ("1" = ETH
// mainnet, "0" = BTC; testnet ids differ).
func WithChains(chains ...string) InterchainOption {
	return func(c *interchainConfig) { c.chains = chains }
}

// InterchainQuery builds the "?perChain=...&chains=..." suffix for the interchain
// trace endpoints. Returns "" when no options are set (the server then applies
// its defaults: one anchor per chain, all chains).
func InterchainQuery(opts ...InterchainOption) string {
	cfg := &interchainConfig{}
	for _, o := range opts {
		o(cfg)
	}

	var parts []string
	if cfg.perChain != nil {
		parts = append(parts, "perChain="+strconv.Itoa(*cfg.perChain))
	}
	if len(cfg.chains) > 0 {
		escaped := make([]string, len(cfg.chains))
		for i, c := range cfg.chains {
			escaped[i] = url.QueryEscape(c)
		}
		parts = append(parts, "chains="+strings.Join(escaped, ","))
	}
	if len(parts) == 0 {
		return ""
	}
	return "?" + strings.Join(parts, "&")
}