package catalogue

import (
	"bytes"
	"encoding/json"
	"fmt"
	"strings"
)

// Decode reads a manifest leniently, as every part but the judge reads one (novox/hq ADR 0578 §3): every field the
// contract knows as it declares it, and a field it does not know set aside and named (SetAside), never refused. It
// judges nothing: no name, seat, bus or catalogue rule is applied, since the indexer judged the manifest once and its
// verdict is in the indexer's state (delivery.VerdictsBucket); a reader takes the verdict beside it
// (delivery.TakeVerdict). An error is only bytes that are no manifest: not JSON, a field of the wrong shape, or one field
// given twice in one object at any depth, named by its path: a decoder keeps the last of two equal keys without a word,
// so a merge of two branches that each added the field would lose one side silently (as mesh-catalog's checks/manifests
// refuses it).
func Decode(raw []byte) (Manifest, error) {
	var m Manifest
	if err := json.Unmarshal(raw, &m); err != nil {
		return Manifest{}, err
	}
	if twice := givenTwice(raw); twice != "" {
		return Manifest{}, fmt.Errorf("the field %s is given twice; a manifest gives each field once", twice)
	}
	return m, nil
}

// givenTwice is the first field an object of raw gives twice, as its path (`invokes`, `build.artifacts[0].env`), or empty.
func givenTwice(raw []byte) string {
	d := json.NewDecoder(bytes.NewReader(raw))
	var walk func(path string) string
	walk = func(path string) string {
		t, err := d.Token()
		if err != nil {
			return ""
		}
		switch t {
		case json.Delim('{'):
			seen := map[string]bool{}
			for d.More() {
				k, err := d.Token()
				if err != nil {
					return ""
				}
				key, _ := k.(string)
				at := key
				if path != "" {
					at = path + "." + key
				}
				if seen[key] {
					return at
				}
				seen[key] = true
				if twice := walk(at); twice != "" {
					return twice
				}
			}
			_, _ = d.Token()
		case json.Delim('['):
			for i := 0; d.More(); i++ {
				if twice := walk(fmt.Sprintf("%s[%d]", path, i)); twice != "" {
					return twice
				}
			}
			_, _ = d.Token()
		}
		return ""
	}
	return walk("")
}

// SetAside names what Decode set aside of this manifest: each field it does not know, as the decoder words the first
// and with the path of every one it read without, or "" when it knew every field. A reader says it in its own words
// (its journal, its finding) and reads the rest; the part that needs the field takes the newer package (ADR 0578 §6).
func (m Manifest) SetAside() string { return m.unknown }

// ReadNoFurther is whether Decode could not read past a field it does not know, so the manifest holds its name and
// version alone: a reader holds such a module, as it holds a refused one, and names why (SetAside).
func (m Manifest) ReadNoFurther() bool { return strings.Contains(m.unknown, readNoFurther) }

// readNoFurther marks, in what a manifest set aside, that it was not read past it.
const readNoFurther = "(read no further: "

// Predefined is the list of predefined keys the manifest was read with (ReadTreeManifestWritten, or the judge's
// SetPredefined), nil when none: data of the contract a judge reads, never a rule.
func (m Manifest) Predefined() PredefinedList { return m.predefined }

// SetPredefined keeps the list of predefined keys a manifest is read with, for what reads it after (the judge).
func (m *Manifest) SetPredefined(list PredefinedList) { m.predefined = list }

// FormsWritten is the fields the manifest's config was written with, in the config form (`config`, `takes-config`,
// `${config:…}`) and in the settings form (novox/hq ADR 0348 §1): data a judge reads to say a manifest mixes them.
func (m Manifest) FormsWritten() (config, settings []string) { return m.forms.config, m.forms.settings }