// Package acme turns "publish (or remove) this DNS-01 challenge value"
// into record changes. The jarl CLI (jarl acme) and jarld's httpreq
// endpoint for lego both use it, so they behave the same way.
package acme

import (
	"encoding/json"
	"strings"

	"jarl/internal/api"
	"jarl/internal/dnsname"
)

// DefaultTTL is the TTL of challenge records.
const DefaultTTL = 60

// Comment is stored with every challenge record.
const Comment = "ACME DNS-01 challenge"

// Zone is a primary zone that may receive challenge records.
type Zone struct {
	Name string // as Jarl stores it, e.g. "adbraun.lol."
	View string // "" when views are not used
}

// Zones returns the zones that hold name: the longest matching zone, in
// every view that has it, or only in view when view is set. The record is
// written into every view so that the CA (usually in an external view) and
// internal resolvers see the same thing.
func Zones(name string, zones []Zone, view string) []Zone {
	name = dnsname.Fqdn(name)
	best := ""
	var out []Zone
	for _, z := range zones {
		if view != "" && !strings.EqualFold(z.View, view) {
			continue
		}
		zn := dnsname.Fqdn(z.Name)
		if !dnsname.IsSubdomain(name, zn) {
			continue
		}
		switch {
		case len(zn) > len(best):
			best, out = zn, []Zone{z}
		case zn == best:
			out = append(out, z)
		}
	}
	return out
}

// Requests returns the changes that set (or, with set false, remove) the
// TXT values at name in each zone. Setting first deletes the same value, so
// a retried hook succeeds instead of failing on a duplicate record, and
// removing a value that isn't there succeeds too. Removing with no values
// removes every TXT record at name.
func Requests(name string, zones []Zone, values []string, set bool, ttl uint32) []api.ChangeRequest {
	name = dnsname.Fqdn(name)
	var reqs []api.ChangeRequest
	add := func(op string, z Zone, extra map[string]any) {
		m := map[string]any{"zone": z.Name, "name": name, "type": "TXT"}
		if z.View != "" {
			m["view"] = z.View
		}
		for k, v := range extra {
			m[k] = v
		}
		b, _ := json.Marshal(m)
		reqs = append(reqs, api.ChangeRequest{Op: op, Data: b})
	}
	for _, z := range zones {
		if !set && len(values) == 0 {
			add("record.delete", z, map[string]any{"missing_ok": true})
			continue
		}
		for _, v := range values {
			add("record.delete", z, map[string]any{"data": v, "missing_ok": true})
			if set {
				add("record.create", z, map[string]any{"data": v, "ttl": ttl, "comment": Comment})
			}
		}
	}
	return reqs
}

// Description is the changeset description for a change at name.
func Description(name string, set bool) string {
	verb := "remove"
	if set {
		verb = "set"
	}
	return "ACME: " + verb + " challenge for " + dnsname.Display(dnsname.Fqdn(name))
}