package buildstep

import (
	"encoding/json"
	"fmt"
	"slices"
	"strings"
	"time"

	"git.novox.be/novox/mesh-sdk/go/buscalls"
	"git.novox.be/novox/mesh-sdk/go/catalogue"
)

// **The artifact store's holder takes its own new build even when its seat is the one broken** (novox/hq design 47,
// lines 1888-1906 at b33ac325; test 60): when the seat oci-artifact-registry refuses or does not answer the store of a
// trunk build of a module that claims that seat, the build module keeps that build on the bus, one object per build
// named by its digest, and the node-engine composing the holder asks the build seats' verb kept-artifact where it is.
// The judgement the three build modules share is here (ADR 0634 §2): what may be kept, the kept builds a node holds,
// and the verb's answer with its three refusals. The store and the verb's serving are each build module's own.

// StoreSeat is the seat whose holder's builds a build node keeps.
const StoreSeat = "oci-artifact-registry"

// The refusals of kept-artifact, the words of the part build-step's enum.
const (
	KeptRefusedClaimsNoStore = "claims no " + StoreSeat
	KeptRefusedNotKept       = "not kept"
	KeptRefusedDigestDiffers = "digest differs"
)

// CatalogModuleVerb is the seat mesh-catalog's verb that answers one module's manifest, as a manifest invokes it.
const CatalogModuleVerb = "seat:mesh-catalog.module"

// KeptFor is what a build keeps a refused artifact for: the module, which claims the store's seat, and its build's
// fingerprint, which kept-artifact is asked by.
type KeptFor struct{ Module, Fp string }

// KeepOf is the keep of a build, or nil when nothing may be kept: only a trunk build (publish) of a module whose manifest
// at the built commit claims the store's seat, named by its fingerprint.
func KeepOf(publish bool, manifest catalogue.Manifest, fp string) *KeptFor {
	if !publish || fp == "" || !manifest.ClaimsSeat(StoreSeat) {
		return nil
	}
	return &KeptFor{Module: manifest.Module, Fp: fp}
}

// KeptBuild is one kept build: the object's description names its module, fingerprint and the node that kept it.
type KeptBuild struct {
	Module   string    `json:"module"`
	Fp       string    `json:"fp"`
	Node     string    `json:"node"`
	Digest   string    `json:"digest"`
	Bytes    uint64    `json:"bytes"`
	LastUsed time.Time `json:"last-used"`
}

// KeptObject is the object name (the hex digest of "sha256:<hex>") and description a build is kept under on node.
func KeptObject(k KeptFor, node, digest string) (name, description string) {
	desc, _ := json.Marshal(KeptBuild{Module: k.Module, Fp: k.Fp, Node: node})
	return strings.TrimPrefix(digest, "sha256:"), string(desc)
}

// KeptBuildsOf are the builds node keeps among a store's objects, by digest.
func KeptBuildsOf(infos []buscalls.ObjectInfo, node string) []KeptBuild {
	out := []KeptBuild{}
	for _, i := range infos {
		var k KeptBuild
		if i.Deleted || json.Unmarshal([]byte(i.Description), &k) != nil || k.Node != node {
			continue
		}
		k.Digest, k.Bytes, k.LastUsed = i.Name, i.Size, i.Modified.UTC()
		out = append(out, k)
	}
	slices.SortFunc(out, func(a, b KeptBuild) int { return strings.Compare(a.Digest, b.Digest) })
	return out
}

// ClaimsStoreOf reads the seat mesh-catalog's answer of one module (CatalogModuleVerb): whether its manifest claims the
// store's seat; a module the catalog holds no manifest of claims nothing.
func ClaimsStoreOf(module string, raw []byte) (bool, error) {
	var a struct {
		Module struct {
			Manifest json.RawMessage `json:"manifest"`
		} `json:"module"`
	}
	if err := json.Unmarshal(raw, &a); err != nil {
		return false, fmt.Errorf("%s answered what is no module: %w", CatalogModuleVerb, err)
	}
	if len(a.Module.Manifest) == 0 {
		return false, nil
	}
	man, err := catalogue.Decode(a.Module.Manifest)
	if err != nil {
		return false, fmt.Errorf("the manifest of %s: %w", module, err)
	}
	return man.ClaimsSeat(StoreSeat), nil
}

// KeptArtifactAnswer is the verb kept-artifact's answer, the part build-step's layout.
type KeptArtifactAnswer struct {
	Module  string `json:"module"`
	Fp      string `json:"fp"`
	Digest  string `json:"digest,omitempty"`
	Size    int64  `json:"size,omitempty"`
	Store   string `json:"store,omitempty"`
	Object  string `json:"object,omitempty"`
	Refused string `json:"refused,omitempty"`
	Words   string `json:"words,omitempty"`
	Error   string `json:"error,omitempty"`
}

// KeptArtifact answers kept-artifact for module, fp and the hex digest from the builds this node keeps, in store (the
// store's name on the bus); claims asks the seat mesh-catalog whether a module claims the store's seat, only when no
// build of it is kept here at that digest.
func KeptArtifact(module, fp, digest string, kept []KeptBuild, store string, claims func(module string) (bool, error)) KeptArtifactAnswer {
	a := KeptArtifactAnswer{Module: module, Fp: fp}
	var other *KeptBuild
	for i, k := range kept {
		if k.Module != module || k.Fp != fp {
			continue
		}
		if k.Digest == digest {
			a.Digest, a.Size, a.Object = k.Digest, int64(k.Bytes), k.Digest
			if store == "" {
				a.Error = "this module runs with no name of its own (MESH_MODULE), so its store's name on the bus is unknown"
				return a
			}
			a.Store = store
			return a
		}
		other = &kept[i]
	}
	ok, err := claims(module)
	switch {
	case err != nil:
		a.Error = "asking whether " + module + " claims " + StoreSeat + ": " + err.Error()
	case !ok:
		a.Refused = KeptRefusedClaimsNoStore
		a.Words = fmt.Sprintf("%s claims no %s: a build node keeps builds for that seat's holder alone", module, StoreSeat)
	case other != nil:
		a.Refused, a.Digest = KeptRefusedDigestDiffers, other.Digest
		a.Words = fmt.Sprintf("this node keeps the build of %s at %s under the digest %s, not %s", module, fp, other.Digest, digest)
	default:
		a.Refused = KeptRefusedNotKept
		a.Words = fmt.Sprintf("this node keeps no build of %s at %s (never kept, or swept)", module, fp)
	}
	return a
}