package builder

import (
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"net/url"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/novox/mesh-controller/internal/catalogue"
)

// Npmrc is what a build needs to resolve the mesh's own shared library — and any other package the
// mesh publishes — from the mesh's package registry rather than from a git URL (novox/hq ADR 0076,
// issue 053).
//
// It is a build-time credential, not a runtime one. A module compiled inside the toolchain image
// resolves the SDK there, once, when that image is built; the running container never speaks to the
// package registry. So this is given to the *builder*, the way the artifact store is
// (`whereToPublish`), and reaches a build as a secret rather than a layer — see Secret.
//
// The registry's exact URL shape is the provider's business, not the builder's: it arrives whole,
// either from the binding the mesh writes (a package-registry provider's `serves` facts) or from the
// environment when a person runs a build by hand. Nothing here knows gitea from verdaccio.
type Npmrc struct {
	// Scope is the npm scope the registry answers for, e.g. "@novox". A build resolves only this
	// scope from the mesh; everything else resolves the ordinary way, so a mesh with no internet
	// still cannot pull the public registry's version of a name the mesh also publishes.
	Scope string
	// Registry is the full base URL a client uses for this scope, e.g.
	// "https://<forge>/api/packages/<owner>/npm/". Trailing slash tolerated either way.
	Registry string
	// Token authenticates to the registry as a bearer token, when a provider mints one. Left empty
	// when the mesh authenticates the ordinary way it authenticates everything — a generated
	// password it applies and seals — for which see Username and Password.
	Token string
	// Username and Password authenticate by basic auth, which is what gitea and verdaccio both
	// accept and what lets the credential be a mesh-generated password the provider's provisioner
	// applies and the mesh seals to the consumer — the same shape a database password takes. The
	// username is the consumer's mesh identity. Ignored when Token is set.
	Username string
	Password string

	// From says where the build agent resolved this registry from (novox/hq ADR 0336 §4): its
	// npm-package-registry binding, the genesis document the installer sealed to it, or the
	// environment of a builder run by a person. Empty when it resolved none.
	From string
	// Machine is the machine the build agent runs on, named when a build that needs the registry is
	// refused for having none (ADR 0336 §6).
	Machine string
}

// Where a build agent resolves the mesh's package registry from (novox/hq ADR 0336 §3, §4).
const (
	// FromBinding is the npm-package-registry binding the mesh wrote, with the credential it sealed.
	FromBinding = "the npm-package-registry binding"
	// FromGenesis is the genesis document the installer sealed at genesis's packages step, read only
	// while no binding is present.
	FromGenesis = "the genesis document"
	// FromEnvironment is the environment of a builder run by a person.
	FromEnvironment = "the environment"
)

// RegistryRequirement is the build agent's optional requirement the registry is bound through, and
// RegistryProvider the catalogue module that provides it (novox/hq ADR 0336 §1, §6): named when a
// build that needs the registry is refused, so the outcome says what to assign. The controller's
// catalogue test holds the provider to the catalogue's.
const (
	RegistryRequirement = "npm-package-registry"
	RegistryProvider    = "gitea"
)

// Enabled reports whether there is a registry to resolve against at all. A bootstrap build that
// runs before any package registry exists has none, and must still build whatever needs no
// mesh-published dependency.
func (n Npmrc) Enabled() bool {
	return strings.TrimSpace(n.Scope) != "" && strings.TrimSpace(n.Registry) != ""
}

// File renders the .npmrc a build mounts. Two lines: which registry answers for the scope, and the
// token to present to it. The auth line is keyed by the registry URL with its scheme removed, which
// is how npm matches a stored credential to a request.
//
// It returns an error rather than a malformed file, because an .npmrc that npm parses but points
// nowhere fails much later, inside a build, as a package that cannot be found.
func (n Npmrc) File() (string, error) {
	scope := strings.TrimSpace(n.Scope)
	if !strings.HasPrefix(scope, "@") {
		return "", fmt.Errorf("a package-registry scope is written with its leading @, not %q", scope)
	}
	reg := strings.TrimSpace(n.Registry)
	if !strings.HasPrefix(reg, "http://") && !strings.HasPrefix(reg, "https://") {
		return "", fmt.Errorf("a package registry is reached over http(s), and %q is neither", reg)
	}
	if !strings.HasSuffix(reg, "/") {
		// npm's per-scope registry key is matched by prefix, and the auth key below is derived from
		// it; a missing trailing slash makes the two disagree and the token is never sent.
		reg += "/"
	}
	parsed, err := url.Parse(reg)
	if err != nil {
		return "", fmt.Errorf("%q is not a usable registry URL: %w", reg, err)
	}
	// The auth key is the URL without its scheme, e.g. "//host/api/packages/owner/npm/".
	authKey := "//" + parsed.Host + parsed.EscapedPath()

	var auth string
	switch {
	case strings.TrimSpace(n.Token) != "":
		auth = fmt.Sprintf("%s:_authToken=%s\n", authKey, strings.TrimSpace(n.Token))
	case strings.TrimSpace(n.Username) != "" && n.Password != "":
		// npm reads the password base64-encoded, and always-auth so it presents the credential to
		// reads as well as writes — a private registry answers neither without it.
		enc := base64.StdEncoding.EncodeToString([]byte(n.Password))
		auth = fmt.Sprintf("%s:username=%s\n%s:_password=%s\n%s:always-auth=true\n",
			authKey, strings.TrimSpace(n.Username), authKey, enc, authKey)
	default:
		return "", fmt.Errorf(
			"the package registry at %s was given neither a token nor a username and password", reg)
	}
	return fmt.Sprintf("%s:registry=%s\n%s", scope, reg, auth), nil
}

// needsRegistry says why this module's build needs the mesh's package registry, or "" when it needs
// none (novox/hq ADR 0336 §5): a `package` artifact, an image whose Dockerfile names .npmrc, or a
// TypeScript artifact with an `@novox/` dependency. Every Go artifact, every image that does not name
// .npmrc, and every image pulled upstream builds without it.
func needsRegistry(manifest catalogue.Manifest, within string) (string, error) {
	if manifest.Build == nil {
		return "", nil
	}
	for _, a := range manifest.Build.Artifacts {
		switch {
		case a.Kind == catalogue.ArtifactPackage:
			return fmt.Sprintf("%s is a package, published to the registry", a.Name), nil
		case a.Kind == catalogue.ArtifactImage:
			raw, err := os.ReadFile(filepath.Join(within, a.From))
			if err == nil && strings.Contains(string(raw), ".npmrc") {
				return fmt.Sprintf("%s's Dockerfile names .npmrc", a.Name), nil
			}
		case a.Language == "typescript":
			scoped, err := scopedDependencies(within)
			if err != nil {
				return "", err
			}
			if len(scoped) > 0 {
				return fmt.Sprintf("%s is TypeScript and depends on %s", a.Name, strings.Join(scoped, ", ")), nil
			}
		}
	}
	return "", nil
}

// scopedDependencies is every `@novox/` package the module's package.json depends on, the SDK
// included.
func scopedDependencies(tree string) ([]string, error) {
	raw, err := os.ReadFile(filepath.Join(tree, "package.json"))
	if errors.Is(err, os.ErrNotExist) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	var p struct {
		Dependencies map[string]string `json:"dependencies"`
	}
	if err := json.Unmarshal(raw, &p); err != nil {
		return nil, fmt.Errorf("the module's package.json is not JSON: %w", err)
	}
	var names []string
	for name := range p.Dependencies {
		if strings.HasPrefix(name, "@novox/") {
			names = append(names, name)
		}
	}
	sort.Strings(names)
	return names, nil
}

// unbound is the refusal of a build that needs the registry on a build agent that has none (novox/hq
// ADR 0336 §6): it names the machine, the requirement left unbound there and the module that provides
// it. Nothing is built, nothing is published, and the `@novox` scope is never resolved from the
// public registry instead.
func (n Npmrc) unbound(module, why string) error {
	machine := n.Machine
	if machine == "" {
		machine = "this machine"
	}
	return fmt.Errorf("%s needs the mesh's package registry (%s), and %s is unbound on %s: the build "+
		"agent there has neither its binding nor the genesis document. It is provided by the %s module; "+
		"once %s is assigned the requirement binds (novox/hq ADR 0336 §6)",
		module, why, RegistryRequirement, machine, RegistryProvider, RegistryProvider)
}

// packageRecipe is how a `package` artifact is built and published: on a PUBLIC base image, never
// the mesh toolchain, because the toolchain is built from the package this produces (the SDK). The
// script builds the module, then publishes it to the mesh's package registry unless that exact
// version is already there — so a re-run of genesis, which must be safe, does not fail on a version
// it published a moment ago.
type packageRecipe struct {
	Base   string
	Script string
}

var packageRecipes = map[string]packageRecipe{
	"typescript": {
		Base: "node:22-bookworm-slim",
		Script: `set -e
npm install --no-audit --no-fund
npm run build
name="$(node -p "require('./package.json').name")"
ver="$(node -p "require('./package.json').version")"
if npm view "$name@$ver" version >/dev/null 2>&1; then
  echo "mesh-builder: $name@$ver is already published, leaving it"
else
  npm publish
fi`,
	},
}

// PackageLanguages is the languages a package artifact can be written in, for a manifest check that
// wants to refuse one it cannot build before a build starts.
func PackageLanguages() []string {
	out := make([]string, 0, len(packageRecipes))
	for l := range packageRecipes {
		out = append(out, l)
	}
	return out
}