package testkit

import (
	"encoding/base64"
	"encoding/hex"
	"fmt"
	"strings"
	"time"

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

// SpecVersion is the specification the vectors and fixtures implement.
const SpecVersion = "0.8.1"

// RoundVector is one Quicknet resolution vector (spec §65).
type RoundVector struct {
	Name      string `json:"name"`
	Requested string `json:"requested"`
	Round     uint64 `json:"round,omitempty"`
	Effective string `json:"effective,omitempty"`
	Error     string `json:"error,omitempty"`
}

// RoundVectorFile is testdata/vectors/quicknet_rounds.json.
type RoundVectorFile struct {
	Spec        string        `json:"spec"`
	Profile     string        `json:"profile"`
	Description string        `json:"description"`
	Vectors     []RoundVector `json:"vectors"`
}

// DK1Vector is one dk1_ vector (spec §66). Valid vectors carry the logical
// object and every intermediate encoding; invalid ones carry the input and the
// expected error.
type DK1Vector struct {
	Name          string `json:"name"`
	Network       string `json:"network,omitempty"`
	Round         uint64 `json:"round,omitempty"`
	CanonicalJSON string `json:"canonical_json,omitempty"`
	Base64URL     string `json:"base64url,omitempty"`
	Input         string `json:"input,omitempty"`
	DK1           string `json:"dk1,omitempty"`
	Error         string `json:"error,omitempty"`
}

// DK1VectorFile is testdata/vectors/dk1.json.
type DK1VectorFile struct {
	Spec        string      `json:"spec"`
	Description string      `json:"description"`
	Vectors     []DK1Vector `json:"vectors"`
}

// ProfileVector is testdata/vectors/profile_quicknet.json.
type ProfileVector struct {
	Spec          string `json:"spec"`
	Description   string `json:"description"`
	ProfileID     string `json:"profile_id"`
	Provider      string `json:"provider"`
	Network       string `json:"network"`
	ChainHash     string `json:"chain_hash"`
	PublicKey     string `json:"public_key"`
	PeriodSeconds uint64 `json:"period_seconds"`
	GenesisTime   int64  `json:"genesis_time"`
	GenesisSeed   string `json:"genesis_seed"`
	Scheme        string `json:"scheme"`
	CanonicalCBOR string `json:"canonical_cbor"`
	ProfileHash   string `json:"profile_hash"`
}

// RoundVectors computes the Quicknet resolution vectors with the implementation.
func RoundVectors() RoundVectorFile {
	p := profile.Quicknet()
	g := time.Unix(p.GenesisTime, 0).UTC()
	r1000, _ := datekey.RoundTime(p, 1000)
	cases := []struct {
		name string
		at   time.Time
	}{
		{"genesis exactly: round 1", g},
		{"genesis + 1ns: next round", g.Add(time.Nanosecond)},
		{"genesis + 1s", g.Add(time.Second)},
		{"genesis + one period: round 2", g.Add(3 * time.Second)},
		{"genesis + one period + 1ns: round 3", g.Add(3*time.Second + time.Nanosecond)},
		{"genesis - 1s: before the profile", g.Add(-time.Second)},
		{"round 1000 boundary exactly", r1000},
		{"one second before the round 1000 boundary", r1000.Add(-time.Second)},
		{"one second after the round 1000 boundary", r1000.Add(time.Second)},
		{"1ns after the round 1000 boundary", r1000.Add(time.Nanosecond)},
		{"half a second after the round 1000 boundary", r1000.Add(500 * time.Millisecond)},
		{"normative vector 2030-01-01 (spec §16)", time.Date(2030, 1, 1, 0, 0, 0, 0, time.UTC)},
		{"1ns after 2030-01-01", time.Date(2030, 1, 1, 0, 0, 0, 1, time.UTC)},
		{"normative vector round 66432123 (spec §16)", time.Date(2029, 12, 16, 7, 15, 33, 0, time.UTC)},
		{"offset timezone equals UTC instant", time.Date(2026, 10, 22, 19, 0, 0, 1_000_000, time.FixedZone("", 2*3600))},
		{"last representable round time", time.Date(9999, 12, 31, 23, 59, 57, 0, time.UTC)},
		{"after the last representable round", time.Date(9999, 12, 31, 23, 59, 59, 0, time.UTC)},
	}
	f := RoundVectorFile{
		Spec:        SpecVersion,
		Profile:     p.ID,
		Description: "Quicknet date to round resolution (spec §15, §16, §65), generated by the reference implementation.",
	}
	for _, c := range cases {
		v := RoundVector{Name: c.name, Requested: c.at.Format(time.RFC3339Nano)}
		d, err := datekey.Resolve(p, c.at)
		if err != nil {
			v.Error = datekeys.Code(err)
		} else {
			v.Round = d.Round
			v.Effective = d.UnlockAt(p).Format(time.RFC3339Nano)
		}
		f.Vectors = append(f.Vectors, v)
	}
	return f
}

// DK1Vectors computes the dk1_ vectors with the implementation.
func DK1Vectors() DK1VectorFile {
	f := DK1VectorFile{
		Spec:        SpecVersion,
		Description: "Canonical dk1_ strings and rejected encodings (spec §18, §19, §66), generated by the reference implementation.",
	}
	for _, v := range []struct {
		name  string
		round uint64
	}{
		{"round 1", 1},
		{"round 1000", 1000},
		{"normative 2030-01-01 round", 66884212},
		{"last Quicknet round", profile.Quicknet().MaxRound()},
	} {
		d := datekey.DateKey{ProfileID: profile.QuicknetID, Round: v.round}
		j := d.CanonicalJSON()
		f.Vectors = append(f.Vectors, DK1Vector{
			Name:          v.name,
			Network:       d.ProfileID,
			Round:         d.Round,
			CanonicalJSON: string(j),
			Base64URL:     base64.RawURLEncoding.EncodeToString(j),
			DK1:           d.Compact(),
		})
	}
	enc := func(s string) string { return datekey.Prefix + base64.RawURLEncoding.EncodeToString([]byte(s)) }
	canon := datekey.DateKey{ProfileID: profile.QuicknetID, Round: 66884212}
	// The canonical JSON of round 1000 is 59 bytes: its Base64 form needs padding
	// and has unused bits, unlike the 63-byte JSON of round 66884212.
	r1000 := datekey.DateKey{ProfileID: profile.QuicknetID, Round: 1000}
	bad := []struct{ name, input string }{
		{"whitespace in JSON", enc(`{"version": 1, "network": "datekeys:quicknet:v1", "round": 66884212}`)},
		{"keys reordered", enc(`{"network":"datekeys:quicknet:v1","version":1,"round":66884212}`)},
		{"trailing whitespace", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":66884212}` + "\n")},
		{"exponent notation", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":6.6884212e7}`)},
		{"fraction notation", enc(`{"version":1.0,"network":"datekeys:quicknet:v1","round":66884212}`)},
		{"escaped character", enc(strings.Replace(string(canon.CanonicalJSON()), "datekeys:", "datekeys\\"+"u003a", 1))},
		{"duplicate key", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":1,"round":66884212}`)},
		{"padded Base64URL", datekey.Prefix + base64.URLEncoding.EncodeToString(r1000.CanonicalJSON())},
		{"non-zero trailing bits", mangleLastChar(r1000.Compact())},
		{"extra field", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":66884212,"public_key":"00"}`)},
		{"missing field", enc(`{"version":1,"network":"datekeys:quicknet:v1"}`)},
		{"version 2", enc(`{"version":2,"network":"datekeys:quicknet:v1","round":66884212}`)},
		{"round 0", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":0}`)},
		{"negative round", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":-1}`)},
		{"fractional round", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":1.5}`)},
		{"round above 2^53-1", enc(fmt.Sprintf(`{"version":1,"network":"datekeys:quicknet:v1","round":%d}`, uint64(datekey.MaxRound)+1))},
		{"round as string", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":"66884212"}`)},
		{"uppercase network", enc(`{"version":1,"network":"DATEKEYS:QUICKNET:V1","round":66884212}`)},
		{"trailing data", enc(`{"version":1,"network":"datekeys:quicknet:v1","round":66884212}x`)},
		{"byte order mark", enc("\ufeff" + `{"version":1,"network":"datekeys:quicknet:v1","round":66884212}`)},
		{"not Base64", datekey.Prefix + "!!!"},
		{"missing prefix", canon.Compact()[len(datekey.Prefix):]},
		{"uppercase prefix", "DK1_" + canon.Compact()[len(datekey.Prefix):]},
	}
	for _, b := range bad {
		_, err := datekey.Parse(b.input)
		code := datekeys.Code(err)
		if err == nil {
			code = "accepted"
		}
		f.Vectors = append(f.Vectors, DK1Vector{Name: b.name, Input: b.input, Error: code})
	}
	return f
}

// mangleLastChar changes the last Base64 character to one that decodes to the
// same bytes but has non-zero unused bits.
func mangleLastChar(s string) string {
	const alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
	last := s[len(s)-1]
	for i := 0; i < len(alphabet); i++ {
		c := alphabet[i]
		if c == last {
			continue
		}
		cand := s[:len(s)-1] + string(c)
		a, errA := base64.RawURLEncoding.DecodeString(s[len(datekey.Prefix):])
		b, errB := base64.RawURLEncoding.DecodeString(cand[len(datekey.Prefix):])
		if errA == nil && errB == nil && string(a) == string(b) {
			return cand
		}
	}
	return s
}

// QuicknetProfileVector computes the profile vector with the implementation.
func QuicknetProfileVector() (ProfileVector, error) {
	p := profile.Quicknet()
	b, err := p.CanonicalCBOR()
	if err != nil {
		return ProfileVector{}, err
	}
	h, err := p.Hash()
	if err != nil {
		return ProfileVector{}, err
	}
	return ProfileVector{
		Spec:          SpecVersion,
		Description:   "Quicknet Provider Profile V1: exact Deterministic CBOR and profile_hash (spec §11, §12, §75 item 2), generated by the reference implementation.",
		ProfileID:     p.ID,
		Provider:      p.Provider,
		Network:       p.Network,
		ChainHash:     p.ChainHashHex(),
		PublicKey:     hex.EncodeToString(p.PublicKey),
		PeriodSeconds: uint64(p.Period / time.Second),
		GenesisTime:   p.GenesisTime,
		GenesisSeed:   hex.EncodeToString(p.GenesisSeed[:]),
		Scheme:        p.Scheme,
		CanonicalCBOR: hex.EncodeToString(b),
		ProfileHash:   hex.EncodeToString(h[:]),
	}, nil
}