// Package testkit builds DateKeys test material: known Quicknet releases,
// offline release sources, capsules with arbitrary structural defects, and age
// files with edited headers whose MAC is still valid.
//
// It is internal and exists for tests and fixture generation only.
package testkit

import (
	"context"
	"encoding/hex"
	"fmt"
	"time"

	datekeys "github.com/datekeys/datekeys-go"
	"github.com/datekeys/datekeys-go/profile"
	"github.com/datekeys/datekeys-go/provider"
)

// Published Quicknet signatures. They are public data obtained from drand
// relays; tests never trust them blindly but verify them with provider.Verify
// against the pinned public key.
var signatures = map[uint64]string{
	1000: "b44679b9a59af2ec876b1a6b1ad52ea9b1615fc3982b19576350f93447cb1125e342b73a8dd2bacbe47e4b6b63ed5e39",
	1001: "b33bf3667cbd5a82de3a24b4e0e9fe5513cc1a0e840368c6e31f5fcfa79bea03f73896b25883abf2853d10337fb8fa41",
	2000: "b6cb8f482a0b15d45936a4c4ea08e98a087e71787caee3f4d07a8a9843b1bc5423c6b3c22f446488b3137eaca799c77e",
}

// Rounds with a known release, in increasing order.
var Rounds = []uint64{1000, 1001, 2000}

// Release returns the published release of round; it panics for rounds
// without a known signature.
func Release(round uint64) provider.Release {
	s, ok := signatures[round]
	if !ok {
		panic(fmt.Sprintf("testkit: no known release for round %d", round))
	}
	b, err := hex.DecodeString(s)
	if err != nil {
		panic(err)
	}
	return provider.Release{Round: round, Signature: b}
}

// Source serves the given releases by round and reports every other round as
// unavailable. It counts the requests it receives.
type Source struct {
	Releases map[uint64]provider.Release
	Calls    int
}

// NewSource returns a Source with the given releases.
func NewSource(releases ...provider.Release) *Source {
	s := &Source{Releases: map[uint64]provider.Release{}}
	for _, r := range releases {
		s.Releases[r.Round] = r
	}
	return s
}

// Fetch implements provider.ReleaseSource.
func (s *Source) Fetch(_ context.Context, _ *profile.Profile, c provider.Condition) (provider.Release, error) {
	s.Calls++
	r, ok := s.Releases[c.Round]
	if !ok {
		return provider.Release{}, fmt.Errorf("testkit: round %d: %w", c.Round, datekeys.ErrReleaseUnavailable)
	}
	return r, nil
}

// Fixed returns a clock stopped at t.
func Fixed(t time.Time) func() time.Time { return func() time.Time { return t } }

// Genesis returns the Quicknet genesis instant, a convenient "now" for
// encrypting to rounds that are already published.
func Genesis() time.Time { return time.Unix(profile.QuicknetGenesisTime, 0).UTC() }

// Registry returns the default registry or panics.
func Registry() profile.Registry {
	r, err := profile.Default()
	if err != nil {
		panic(err)
	}
	return r
}