package chain

import (
	"crypto/sha256"
	"encoding/hex"
	"slices"
	"strings"
)

// The builds bucket's keys (novox/hq issue 1121). A build is under its module, so a read of one module is a read of the keys
// `<module>.>` and no other, and a lookup that has what it looks up by is one Get of a pointer key, whose value is a build's id.
//
//	<module>.build.<id>        a build's record, its outcome (a records-only read is the filter `<module>.build.>`)
//	req.<id>                   a request, and a build that knew no module
//	id.<id>                    the module of the build with that id (the pointer a lookup by id alone reads)
//	<module>.newest            the newest build of the module, of any state
//	<module>.worked            the newest successful build of the module
//	<module>.held              the build standing for the module's newest successful build (issue 280)
//	<module>.commit.<sha>      the newest successful build from that commit: a CommitPointer
//	<module>.source.<key>      the newest successful build with that reuse key (ADR 0350 §1), spelled by SpellReuse
//	manifest.sha256-<hex>      a manifest, once, by the digest of its bytes
//
// **A pointer is a hint** (issue 1121): the record is written first, then each pointer by compare-and-set; a reader Gets the
// record a pointer names and checks it, and when the pointer is missing or wrong reads the module's records, repairs the
// pointers and says so.
//
// No module's name contains a dot. A key is never removed (ADR 0408 §4); the bare `<id>` keys of before the move stay, and are
// never read once the kind `builds-layout` is moved.
const (
	RequestPrefix = "req"
	IDPrefix      = "id"
)

// BuildKey is a build's record under its module; a build that knew none is the request's key.
func BuildKey(module, id string) string {
	if module == "" {
		return RequestKey(id)
	}
	return module + ".build." + id
}

func RequestKey(id string) string         { return RequestPrefix + "." + id }
func IDKey(id string) string              { return IDPrefix + "." + id }
func NewestKey(module string) string      { return module + ".newest" }
func WorkedKey(module string) string      { return module + ".worked" }
func HeldKey(module string) string        { return module + ".held" }
func CommitKey(module, sha string) string { return module + ".commit." + sha }
func SourceKey(module, fp string) string  { return module + ".source." + fp }
func ModuleFilter(module string) string   { return module + ".build.>" }

// ManifestPrefix is where a build's manifest is kept, in the builds bucket itself: a new bucket needs a grant the bus gets
// only at a later push, and the push needs the builds. No module is named so.
const ManifestPrefix = "manifest"

// ReservedModules are the names that are not a module's: a key under one is not a build's record.
var ReservedModules = []string{ManifestPrefix, RequestPrefix, IDPrefix, LayoutPrefix}

// LayoutPrefix is the name of the key that says the builds are laid out under their modules: LayoutMarkerKey, written once by
// the controller's start after it has laid the old keys out. Nothing reads the builds before it exists.
const LayoutPrefix = "layout"

// LayoutMarkerKey is the key whose existence says the layout is made.
const LayoutMarkerKey = LayoutPrefix + ".done"

// ManifestKey is where a manifest is kept: `manifest.sha256-<hex of its bytes>`.
func ManifestKey(raw []byte) string {
	sum := sha256.Sum256(raw)
	return ManifestPrefix + ".sha256-" + hex.EncodeToString(sum[:])
}

// CommitPointer is the value of `<module>.commit.<sha>`: the build, and what the surveys of every module's commits read
// without a Get of each build: its source fingerprint and what it would put on a machine.
type CommitPointer struct {
	Build       string `json:"build"`
	Source      string `json:"source,omitempty"`
	Fingerprint string `json:"fingerprint,omitempty"`
}

// IsRecordKey is whether a key of the builds bucket is a build's record under a module: `<module>.build.<id>`.
func IsRecordKey(key string) bool {
	parts := strings.Split(key, ".")
	return len(parts) == 3 && parts[1] == "build" && !slices.Contains(ReservedModules, parts[0])
}

// SpellReuse is a reuse key (`v1:<hex>`) as a part of a key the bus takes: every character it does not take becomes `-`.
func SpellReuse(key string) string {
	return strings.Map(func(r rune) rune {
		if r >= 'a' && r <= 'z' || r >= 'A' && r <= 'Z' || r >= '0' && r <= '9' || r == '-' || r == '_' {
			return r
		}
		return '-'
	}, key)
}

// ModuleOf is the module a record key is under.
func ModuleOf(key string) string { m, _, _ := strings.Cut(key, "."); return m }

// DecodeKept is a watched entry as a typed record, for a read that took the entries of several kinds and decodes those
// that hold a record.
func DecodeKept[T any](e Entry) (Kept[T], error) { return decode[T](e) }

// AsAnswered is the state of a request record whose outcome has been heard: the record keeps the request and says which
// build answered it, so a read of the requests needs no read of the builds.
const BuildAnswered = "answered"