package engine

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"errors"

	"jarl/internal/model"
	"jarl/internal/nscheck"
	"jarl/internal/render"
	"jarl/internal/store"
)

// viewKeySeedMeta is where the seed of the view keys is kept.
const viewKeySeedMeta = "view_key_seed"

// ViewKeySeed returns the seed the view keys' secrets are derived from
// (render/viewkeys.go), creating it the first time.
func ViewKeySeed(ctx context.Context, st *store.Store) ([]byte, error) {
	v, err := st.GetMeta(ctx, viewKeySeedMeta)
	if err == nil {
		return base64.StdEncoding.DecodeString(v)
	}
	if !errors.Is(err, store.ErrNotFound) {
		return nil, err
	}
	seed := make([]byte, 32)
	if _, err := rand.Read(seed); err != nil {
		return nil, err
	}
	if err := st.SetMeta(ctx, viewKeySeedMeta, base64.StdEncoding.EncodeToString(seed)); err != nil {
		return nil, err
	}
	return seed, nil
}

// extras returns what jarld's configuration adds to the rendered
// configuration, with the view keys' seed.
func (e *Engine) extras(ctx context.Context) render.Extras {
	x := e.cfg.Extras
	e.seedMu.Lock()
	defer e.seedMu.Unlock()
	if e.seed == nil {
		seed, err := ViewKeySeed(ctx, e.store)
		if err != nil {
			e.log.Warn("view keys: reading their seed failed", "err", err)
			return x
		}
		e.seed = seed
	}
	x.ViewKeySeed = e.seed
	return x
}

// ViewKey returns the TSIG key that selects a zone's view on this server
// (nil without views).
func (e *Engine) ViewKey(ctx context.Context, st *model.State, z *model.Zone) *nscheck.Key {
	v := st.Views[z.ViewID]
	if v == nil {
		return nil
	}
	x := e.extras(ctx)
	if len(x.ViewKeySeed) == 0 {
		return nil
	}
	return &nscheck.Key{Name: render.ViewKeyName(v.Name), Algorithm: render.ViewKeyAlgorithm, Secret: render.ViewKeySecret(x.ViewKeySeed, v.ID)}
}

// GeneratedStatements lists what Jarl adds to named.conf by itself
// (render.GeneratedStatements).
func (e *Engine) GeneratedStatements(ctx context.Context, st *model.State) []render.Generated {
	return render.GeneratedStatements(st, e.cfg.Paths, e.extras(ctx))
}