package kubeedit

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"fmt"
	"strings"

	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"

	"git.k8s-git-k6n.net/mats/fancy-dns/internal/kubesource"
)

// objectName turns a DNS name into a Kubernetes object name. Most names are
// already one; a name that is not (an underscore, say) is cleaned and given a
// short hash so two different names cannot collide.
func objectName(domain string) string {
	var b strings.Builder
	changed := false
	for _, c := range domain {
		if c >= 'a' && c <= 'z' || c >= '0' && c <= '9' || c == '-' || c == '.' {
			b.WriteRune(c)
		} else {
			b.WriteByte('-')
			changed = true
		}
	}
	name := strings.Trim(b.String(), "-.")
	if name == "" {
		name, changed = "root", true
	}
	if changed {
		sum := sha256.Sum256([]byte(domain))
		name += "-" + hex.EncodeToString(sum[:3])
	}
	return name
}

func (e *Editor) overrideObjects(ctx context.Context) ([]unstructured.Unstructured, error) {
	return e.list(ctx, kubesource.OverrideGVR)
}

// Overrides lists the address overrides, one entry per name.
func (e *Editor) Overrides(ctx context.Context) ([]kubesource.Override, error) {
	items, err := e.overrideObjects(ctx)
	if err != nil {
		return nil, err
	}
	var out []kubesource.Override
	for i := range items {
		var s kubesource.AddressOverrideSpec
		if decodeSpec(&items[i], &s) != nil {
			continue
		}
		if o, err := kubesource.CheckOverride(s); err == nil {
			out = append(out, o)
		}
	}
	return out, nil
}

// SetOverride makes domain (and everything under it) answer with address,
// replacing whatever it answered with before.
func (e *Editor) SetOverride(ctx context.Context, domain, address, actor string) error {
	o, err := kubesource.CheckOverride(kubesource.AddressOverrideSpec{Domain: domain, Addresses: []string{address}})
	if err != nil {
		return err
	}
	name := objectName(o.Domain)
	items, err := e.overrideObjects(ctx)
	if err != nil {
		return err
	}
	for i := range items {
		var s kubesource.AddressOverrideSpec
		if decodeSpec(&items[i], &s) == nil {
			if have, err := kubesource.CheckOverride(s); err == nil && have.Domain == o.Domain {
				name = items[i].GetName() // keep the object an operator may have named by hand
				break
			}
		}
	}
	if err := checkName("address override", name); err != nil {
		return err
	}
	_, err = e.upsert(ctx, kubesource.OverrideGVR, "AddressOverride", name, actor,
		kubesource.AddressOverrideSpec{Domain: o.Domain, Addresses: o.Addresses})
	return err
}

// DeleteOverride removes the override for domain.
func (e *Editor) DeleteOverride(ctx context.Context, domain string) error {
	want := strings.TrimSuffix(strings.ToLower(strings.TrimSpace(domain)), ".")
	items, err := e.overrideObjects(ctx)
	if err != nil {
		return err
	}
	removed := false
	for i := range items {
		var s kubesource.AddressOverrideSpec
		if decodeSpec(&items[i], &s) != nil {
			continue
		}
		if have, err := kubesource.CheckOverride(s); err == nil && have.Domain == want {
			if err := e.remove(ctx, kubesource.OverrideGVR, items[i].GetName()); err != nil {
				return err
			}
			removed = true
		}
	}
	if !removed {
		return fmt.Errorf("%w: no address override for %s", ErrNotFound, want)
	}
	return nil
}