package automation

import (
	"fmt"
	"strings"
)

// PrefixProxyNames rewrites every proxy's "name" field in data["proxies"]
// and every proxy-group's "name" field in data["proxy-groups"] — both are
// scoped per-subscription and would otherwise collide across subscriptions
// the same way proxy names do — prefixing them with subscriptionName. It
// also rewrites every reference to a renamed proxy or proxy-group inside
// each group's own "proxies" list and inside data["rules"]' rule targets
// (e.g. "DOMAIN,example.com,Proxy" or "MATCH,Auto"), since those are all
// resolved by name and would otherwise silently point at nothing after the
// rename. References to anything else (DIRECT, REJECT, a proxy-provider
// name, ...) are left untouched.
//
// Returns a ProxyRef per proxy, for later ssm matching/grouping.
func PrefixProxyNames(subscriptionName string, data map[string]interface{}) []ProxyRef {
	// Original name (of either a proxy or a proxy-group) -> prefixed
	// display name. Clash requires proxy and group names to share a single
	// namespace within one config, so a single map is correct here too.
	rename := make(map[string]string)

	refs := renameProxies(subscriptionName, data, rename)
	renameProxyGroups(subscriptionName, data, rename)
	rewriteGroupProxyReferences(data, rename)
	rewriteRuleTargets(data, rename)

	return refs
}

func renameProxies(subscriptionName string, data map[string]interface{}, rename map[string]string) []ProxyRef {
	proxiesRaw, ok := data["proxies"].([]interface{})
	if !ok {
		return nil
	}

	refs := make([]ProxyRef, 0, len(proxiesRaw))
	for _, item := range proxiesRaw {
		proxy, ok := item.(map[string]interface{})
		if !ok {
			continue
		}
		name, ok := proxy["name"].(string)
		if !ok {
			continue
		}

		display := fmt.Sprintf("%s | %s", subscriptionName, name)
		proxy["name"] = display
		rename[name] = display

		refs = append(refs, ProxyRef{
			OriginalName: name,
			DisplayName:  display,
			Subscription: subscriptionName,
		})
	}
	return refs
}

func renameProxyGroups(subscriptionName string, data map[string]interface{}, rename map[string]string) {
	for _, group := range proxyGroupMaps(data) {
		name, ok := group["name"].(string)
		if !ok {
			continue
		}
		display := fmt.Sprintf("%s | %s", subscriptionName, name)
		group["name"] = display
		rename[name] = display
	}
}

func rewriteGroupProxyReferences(data map[string]interface{}, rename map[string]string) {
	for _, group := range proxyGroupMaps(data) {
		proxiesRaw, ok := group["proxies"].([]interface{})
		if !ok {
			continue
		}
		for i, p := range proxiesRaw {
			name, ok := p.(string)
			if !ok {
				continue
			}
			if display, renamed := rename[name]; renamed {
				proxiesRaw[i] = display
			}
		}
	}
}

// rewriteRuleTargets rewrites the target field of every rule in
// data["rules"] that references a renamed proxy or proxy-group. Clash rule
// lines are a comma-separated "TYPE,payload,TARGET[,no-resolve]" (or just
// "MATCH,TARGET" with no payload) — the target is always the last field,
// except for the handful of rule types that allow a trailing "no-resolve"
// modifier, where it's the second-to-last. Lines with no comma at all are
// left untouched (not valid rule syntax to begin with).
func rewriteRuleTargets(data map[string]interface{}, rename map[string]string) {
	rulesRaw, ok := data["rules"].([]interface{})
	if !ok {
		return
	}
	for i, item := range rulesRaw {
		line, ok := item.(string)
		if !ok {
			continue
		}
		rulesRaw[i] = rewriteRuleLine(line, rename)
	}
}

func rewriteRuleLine(line string, rename map[string]string) string {
	body := line
	suffix := ""

	if idx := strings.LastIndex(body, ","); idx != -1 && strings.EqualFold(body[idx+1:], "no-resolve") {
		suffix = "," + body[idx+1:]
		body = body[:idx]
	}

	idx := strings.LastIndex(body, ",")
	if idx == -1 {
		return line
	}

	target := body[idx+1:]
	if display, ok := rename[target]; ok {
		body = body[:idx+1] + display
	}

	return body + suffix
}

// proxyGroupMaps returns data["proxy-groups"]'s entries as maps, skipping
// anything malformed.
func proxyGroupMaps(data map[string]interface{}) []map[string]interface{} {
	groupsRaw, ok := data["proxy-groups"].([]interface{})
	if !ok {
		return nil
	}
	groups := make([]map[string]interface{}, 0, len(groupsRaw))
	for _, item := range groupsRaw {
		if group, ok := item.(map[string]interface{}); ok {
			groups = append(groups, group)
		}
	}
	return groups
}