package profile

import (
	"encoding/hex"
	"fmt"

	datekeys "g.activething.com/go/DateKeys"
)

// Registry resolves a profile_id to a locally trusted Provider Profile. The
// client MUST NOT accept a profile or key supplied by the endpoint that
// delivers the release (spec §13); a Registry is built by the caller from
// pinned data only.
type Registry interface {
	// Lookup returns a copy of the pinned profile for id.
	Lookup(id string) (*Profile, bool)
}

// Pin is a profile together with the profile_hash the caller expects it to
// have (spec §13: the profile hash is known in advance).
type Pin struct {
	Profile *Profile
	Hash    [32]byte
}

type pinned struct {
	profile *Profile
	hash    [32]byte
}

type registry struct {
	m map[string]pinned
}

// NewRegistry validates every profile, checks it against its expected
// profile_hash and returns an immutable registry holding private copies.
func NewRegistry(pins ...Pin) (Registry, error) {
	r := &registry{m: make(map[string]pinned, len(pins))}
	for _, pin := range pins {
		if pin.Profile == nil {
			return nil, fmt.Errorf("profile: nil profile in registry: %w", datekeys.ErrUnknownProfile)
		}
		p := pin.Profile.Clone()
		if err := p.Validate(); err != nil {
			return nil, err
		}
		h, err := p.Hash()
		if err != nil {
			return nil, err
		}
		if h != pin.Hash {
			return nil, fmt.Errorf("profile %s: profile_hash %x does not match the pinned %x: %w",
				p.ID, h, pin.Hash, datekeys.ErrProfileMismatch)
		}
		if _, dup := r.m[p.ID]; dup {
			return nil, fmt.Errorf("profile %s: pinned twice", p.ID)
		}
		r.m[p.ID] = pinned{profile: p, hash: h}
	}
	return r, nil
}

func (r *registry) Lookup(id string) (*Profile, bool) {
	e, ok := r.m[id]
	if !ok {
		return nil, false
	}
	return e.profile.Clone(), true
}

// Default returns the default registry, which contains only the Quicknet
// profile checked against QuicknetProfileHash.
func Default() (Registry, error) {
	var h [32]byte
	b, err := hex.DecodeString(QuicknetProfileHash)
	if err != nil || len(b) != len(h) {
		return nil, fmt.Errorf("profile: invalid pinned Quicknet profile hash: %w", datekeys.ErrProfileMismatch)
	}
	copy(h[:], b)
	return NewRegistry(Pin{Profile: Quicknet(), Hash: h})
}