//go:build ignore

// Writes test/vectors/mutation_texts.json: the text of the error that
// capsule.Open of the Go reference gives for every case of
// testdata/vectors/mutations.json, or "ok" for a capsule that opens, and the
// checks that it records, step by step with their details, so that the
// tests of datekeys-dart require the same text of the opening, byte for
// byte, and not only the same code and step. A port of
// scripts/mutation-go-texts.go of datekeys-ts, over the synced testdata of
// this repository, that of the branch v0.12 of datekeys-go at c531e93.
//
// Each case is replayed as internal/testkit replays the corpus
// (MutationInput.Open), which a program outside the reference cannot
// import: the Quicknet profile pinned, or no profile for the registry
// "empty"; a release source that answers every request with the release of
// the case, or with "testkit: no release" and ERR_RELEASE_UNAVAILABLE; the
// .dkk decoded before, as OpenOptions.AccessKey; the identities of the case;
// the extensions of the case, known at (id, version) and whose data is valid
// only when it is valid_data, with the texts of testkit.KnownExtensions; a
// sink that discards the files; and the clock of the case.
//
// The code and the step of every case are checked against the corpus: a
// case where Go and the corpus disagree is written with go_error and
// go_step, and reported on the standard error, never resolved silently.
//
// Run it in the module of the reference implementation, which it imports,
// without changing anything there, from the datekeys-go next to this
// repository, on the branch v0.12 at c531e93:
//
//	cd ../datekeys-go && go run ../datekeys-dart/tool/mutation_go_texts.go \
//		../datekeys-dart/testdata > ../datekeys-dart/test/vectors/mutation_texts.json
package main

import (
	"bytes"
	"context"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"

	"filippo.io/age"
	datekeys "g.activething.com/go/DateKeys"
	"g.activething.com/go/DateKeys/accesskey"
	"g.activething.com/go/DateKeys/capsule"
	"g.activething.com/go/DateKeys/extension"
	"g.activething.com/go/DateKeys/profile"
	"g.activething.com/go/DateKeys/provider"
)

type corpus struct {
	Spec  string `json:"spec"`
	Cases []struct {
		Name string `json:"name"`
		DKC  struct {
			Base  string              `json:"base"`
			Edits [][]json.RawMessage `json:"edits"`
		} `json:"dkc"`
		DKK        string   `json:"dkk"`
		Identities []string `json:"identities"`
		Release    *struct {
			Round     uint64 `json:"round"`
			Signature string `json:"signature"`
		} `json:"release"`
		Now        string `json:"now"`
		Registry   string `json:"registry"`
		Extensions []struct {
			ID        string `json:"id"`
			Version   uint64 `json:"version"`
			ValidData string `json:"valid_data"`
		} `json:"extensions"`
		Error string `json:"error"`
		Step  int    `json:"step"`
	} `json:"cases"`
}

// caseOut is one case: its name, the text of the error or "ok", the checks
// as [step, name, ok, detail, code], and, when Go disagrees with the corpus,
// what Go gives.
type caseOut struct {
	Name    string  `json:"name"`
	Text    string  `json:"text"`
	Checks  [][]any `json:"checks"`
	GoError string  `json:"go_error,omitempty"`
	GoStep  int     `json:"go_step,omitempty"`
}

type output struct {
	Spec        string    `json:"spec"`
	Generator   string    `json:"generator"`
	Description string    `json:"description"`
	Cases       []caseOut `json:"cases"`
}

// known is testkit.KnownExtensions: an extension.Registry and
// extension.DataValidator with the same texts.
type known []struct {
	id      string
	version uint64
	valid   []byte
}

func (k known) find(id string, version uint64) int {
	for i := range k {
		if k[i].id == id && k[i].version == version {
			return i
		}
	}
	return -1
}

func (k known) Known(id string, version uint64) bool { return k.find(id, version) >= 0 }

func (k known) ValidateData(e extension.Extension) error {
	i := k.find(e.ID, e.Version)
	if i < 0 {
		return fmt.Errorf("extension %s version %d is not known", e.ID, e.Version)
	}
	if !bytes.Equal(k[i].valid, e.Data) {
		return fmt.Errorf("data %x is not %x", e.Data, k[i].valid)
	}
	return nil
}

// source is testkit's singleSource.
type source struct{ release *provider.Release }

func (s source) Fetch(context.Context, *profile.Profile, provider.Condition) (provider.Release, error) {
	if s.release == nil {
		return provider.Release{}, fmt.Errorf("testkit: no release: %w", datekeys.ErrReleaseUnavailable)
	}
	return *s.release, nil
}

// discard is testkit's DiscardSink.
type discard struct{}

func (discard) Begin(*capsule.Head) error          { return nil }
func (discard) Create(int) (io.WriteCloser, error) { return nopCloser{io.Discard}, nil }
func (discard) Commit() error                      { return nil }
func (discard) Abort()                             {}

type nopCloser struct{ io.Writer }

func (nopCloser) Close() error { return nil }

func must[T any](v T, err error) T {
	if err != nil {
		panic(err)
	}
	return v
}

// applyEdits is the reading of testdata/README.md, "Edited files":
// [at, delete, insert] on the offsets of the unmodified base, sorted and not
// overlapping.
func applyEdits(base []byte, edits [][]json.RawMessage) []byte {
	var out []byte
	pos := 0
	for _, e := range edits {
		var at, del int
		var insert string
		if len(e) != 3 || json.Unmarshal(e[0], &at) != nil || json.Unmarshal(e[1], &del) != nil || json.Unmarshal(e[2], &insert) != nil {
			panic("an edit is [at, delete, insert]")
		}
		if at < pos || at+del > len(base) {
			panic("edits out of order or beyond the base")
		}
		out = append(append(out, base[pos:at]...), must(hex.DecodeString(insert))...)
		pos = at + del
	}
	return append(out, base[pos:]...)
}

func main() {
	dir := os.Args[1]
	var c corpus
	if err := json.Unmarshal(must(os.ReadFile(filepath.Join(dir, "vectors", "mutations.json"))), &c); err != nil {
		panic(err)
	}
	out := output{
		Spec:        c.Spec,
		Generator:   "tool/mutation_go_texts.go",
		Description: "The text of the error of capsule.Open for every case of testdata/vectors/mutations.json, or ok for a capsule that opens, and its checks as [step, name, ok, detail, code]; go_error and go_step where Go and the corpus disagree. See the header of tool/mutation_go_texts.go.",
	}
	disagree := 0
	for _, m := range c.Cases {
		var base []byte
		if m.DKC.Base != "" {
			base = must(os.ReadFile(filepath.Join(dir, "fixtures", m.DKC.Base)))
		}
		dkc := applyEdits(base, m.DKC.Edits)
		reg := must(profile.Default())
		if m.Registry == "empty" {
			reg = must(profile.NewRegistry())
		}
		var src source
		if m.Release != nil {
			src.release = &provider.Release{Round: m.Release.Round, Signature: must(hex.DecodeString(m.Release.Signature))}
		}
		now := must(time.Parse(time.RFC3339Nano, m.Now))
		o := capsule.OpenOptions{Registry: reg, Source: src, Now: func() time.Time { return now }, Sink: discard{}}
		if m.Extensions != nil {
			var k known
			for _, x := range m.Extensions {
				k = append(k, struct {
					id      string
					version uint64
					valid   []byte
				}{x.ID, x.Version, must(hex.DecodeString(x.ValidData))})
			}
			o.Extensions = k
		}
		if m.DKK != "" {
			o.AccessKey = must(accesskey.Decode(bytes.NewReader(must(hex.DecodeString(m.DKK)))))
		}
		for _, s := range m.Identities {
			o.Identities = append(o.Identities, must(age.ParseX25519Identity(s)))
		}
		opened, err := capsule.Open(context.Background(), io.Discard, bytes.NewReader(dkc), o)
		text, code, step := "ok", "ok", 0
		if err != nil {
			text, code = err.Error(), datekeys.Code(err)
		}
		co := caseOut{Name: m.Name, Text: text, Checks: [][]any{}}
		for _, ch := range opened.Inspection.Checks {
			co.Checks = append(co.Checks, []any{ch.Step, ch.Name, ch.OK, ch.Detail, ch.Error})
		}
		if err != nil {
			step = opened.Inspection.Checks[len(opened.Inspection.Checks)-1].Step
		}
		if code != m.Error || step != m.Step {
			disagree++
			co.GoError, co.GoStep = code, step
			fmt.Fprintf(os.Stderr, "%s: Go gives %s at step %d, the corpus says %s at step %d\n", m.Name, code, step, m.Error, m.Step)
		}
		out.Cases = append(out.Cases, co)
	}
	fmt.Fprintf(os.Stderr, "%d cases, %d where Go and the corpus disagree\n", len(out.Cases), disagree)
	var b bytes.Buffer
	e := json.NewEncoder(&b)
	e.SetEscapeHTML(false)
	if err := e.Encode(out.Cases); err != nil {
		panic(err)
	}
	// One case per line.
	var sb strings.Builder
	head := func(v any) string {
		var h bytes.Buffer
		enc := json.NewEncoder(&h)
		enc.SetEscapeHTML(false)
		if err := enc.Encode(v); err != nil {
			panic(err)
		}
		return strings.TrimSuffix(h.String(), "\n")
	}
	sb.WriteString("{\n")
	sb.WriteString(` "spec": ` + head(out.Spec) + ",\n")
	sb.WriteString(` "generator": ` + head(out.Generator) + ",\n")
	sb.WriteString(` "description": ` + head(out.Description) + ",\n")
	sb.WriteString(` "cases": [`)
	for i, co := range out.Cases {
		if i > 0 {
			sb.WriteString(",")
		}
		sb.WriteString("\n  " + head(co))
	}
	sb.WriteString("\n ]\n}\n")
	os.Stdout.WriteString(sb.String())
}