package catalogue

import (
	"fmt"
	"sort"
	"strings"
)

// The node's tool runtime, as the catalogue knows it (novox/hq ADR 0175, to-be 38).
//
// **One module is the runtime.** Where it is assigned, one process per machine serves every assigned
// module's tools and every held seat's verbs, on the host side, from the bundles each module's build
// produced — and no module needs a container to reach the bus with its tools. The name is a constant
// rather than a manifest field because a rule turns on it: the composer places the runtime's process
// where this module is, and registration refuses the old pattern once this module exists.

// RuntimeModule is the module that is the node's tool runtime. Mirrored in the broker package,
// which composes a principal of its own for it; the agreement test there holds the two to one string.
const RuntimeModule = "node-tools"

// BundleRoot is where a machine keeps the tools bundles the mesh delivers to it: under the mesh's
// own directory, beside the daemons the host unpacks there, and never where a package manager also
// writes. One directory per module, one per bundle beneath it, at a path that does not move with
// the version — so the runtime's process names each entrypoint once and is restarted, not
// recomposed, when a bundle changes.
const BundleRoot = "/var/lib/mesh/bundles"

// BundleID names the archive resource that delivers one of a module's bundles; prefixed with the
// module like every resource of its own.
func BundleID(bundle string) string { return "bundle-" + bundle }

// BundlePath is where one module's bundle is unpacked on a machine.
func BundlePath(module, bundle string) string { return BundleRoot + "/" + module + "/" + bundle }

// runtimeHere says whether this node's set includes the runtime module, which is what decides
// whether anything about tools changes on the machine (to-be 38 WP2): until the runtime is assigned,
// a node is sent exactly what it was sent before, bundles included, because a bundle nothing loads
// is bytes nobody reads.
func (r Resolution) runtimeHere() bool {
	for _, m := range r.Modules {
		if m.Module == RuntimeModule {
			return true
		}
	}
	return false
}

// bundleArchives is one archive per tools bundle of a module — a bundle the runtime LOADS something
// from — as the host fetches and unpacks any artifact (novox/hq ADR 0175 §3: a module brings its
// tools as a bundle, delivered by the host like any artifact, never an image). A bundle it loads
// nothing from is run rather than loaded: a daemon, a step, the runtime itself — delivered by the
// process that runs it, and not again here.
//
// The source is the kept reference; the per-resource pass that follows routes it through the
// artifact store as this network reaches it now, as it does every image and archive the mesh built.
func bundleArchives(m Manifest) []map[string]any {
	var out []map[string]any
	for _, b := range m.Bundles {
		if len(b.Loads) == 0 {
			continue
		}
		out = append(out, map[string]any{
			"id": BundleID(b.Name), "type": "archive",
			"source": b.Source, "digest": b.Digest,
			"path": BundlePath(m.Module, b.Name),
		})
	}
	return out
}

// RuntimeProcessID names the one process the mesh composes for a machine's runtime; prefixed with
// the runtime module like a resource of its own, because that module is what the host sees it as.
func RuntimeProcessID() string { return "runtime" }

// RuntimeToolModules is the variable the runtime reads the modules it serves from: one
// `<module>=<entrypoint>` per file it loads, comma-separated — several entries may name one module.
// RuntimeBrokerFile is where it reads the node's credential; RuntimeOperatorAccount and
// RuntimeOperatorHome are the machine's operator account and home, handed to every tool's
// environment (to-be 38 WP1), and absent on a machine with no account.
const (
	RuntimeToolModules     = "MESH_TOOL_MODULES"
	RuntimeBrokerFile      = "MESH_BROKER_FILE"
	RuntimeOperatorAccount = "MESH_OPERATOR_ACCOUNT"
	RuntimeOperatorHome    = "MESH_OPERATOR_HOME"
)

// interpreterFor is how a bundle in a language is run: the program the host's unit starts, with the
// bundle's entrypoint after it. The one thing the composer takes from a language, and said here
// rather than in a manifest because the runtime's process is the mesh's to compose (to-be 38 WP3).
func interpreterFor(language string) (string, error) {
	switch language {
	case "typescript":
		return "node", nil
	}
	return "", fmt.Errorf(
		"%s is written in %q, and the mesh knows no interpreter to run a %q bundle with",
		RuntimeModule, language, language)
}

// runtimeProcess is the one process a machine runs the node's tool runtime as (novox/hq ADR 0175,
// to-be 38 WP2.3): the runtime module's own bundle, run by its language's interpreter, told which
// modules it serves and from which files, where its credential is, and who the machine's operator
// is — and restarted when any bundle it loads or the credential it holds changes.
//
// Composed from the placed manifests, so the credential's path is where this node puts it. The
// runtime runs as the operator's account when the machine has one, which is what lets a tool that
// needs root escalate as the operator would (ADR 0175 §4); on a machine with no account it runs as
// root, and the two operator words are not set.
func (r Resolution) runtimeProcess(with Rendering) (map[string]any, error) {
	var runtime *Manifest
	for i := range r.Modules {
		if r.Modules[i].Module == RuntimeModule {
			runtime = &r.Modules[i]
		}
	}
	if runtime == nil {
		return nil, nil
	}
	if len(runtime.Bundles) != 1 {
		return nil, fmt.Errorf(
			"%s is assigned to %s and its build produced %d bundle(s); the runtime is one bundle "+
				"the mesh runs, so the module declares exactly one (novox/hq to-be 38)",
			RuntimeModule, r.Node, len(runtime.Bundles))
	}
	bundle := runtime.Bundles[0]
	if len(bundle.Entrypoints) != 1 {
		return nil, fmt.Errorf(
			"%s's bundle %q names %d entrypoint(s); the runtime is run from one, so the module "+
				"declares exactly one (novox/hq to-be 38)", RuntimeModule, bundle.Name, len(bundle.Entrypoints))
	}
	interpreter, err := interpreterFor(bundle.Language)
	if err != nil {
		return nil, err
	}
	credential, declared := runtime.OwnSecrets["broker"]
	if !declared {
		return nil, fmt.Errorf(
			"%s declares no own secret named broker, and the node's credential is delivered there: "+
				"a module that speaks on the bus declares \"own-secrets\": {\"broker\": <path>}",
			RuntimeModule)
	}

	// What it serves, and from which files: every module on this machine that composes here, in
	// name order, each bundle it loads from in the order the manifest gave. A module left out of
	// the declaration — a filter on an adopted machine — is left out of this too, or the runtime
	// would be told to load files that were never delivered.
	var served []string
	var restartOn []string
	for _, m := range r.Modules {
		if with.Adopted && m.Filtering != nil {
			continue
		}
		for _, b := range m.Bundles {
			if len(b.Loads) == 0 {
				continue
			}
			for _, load := range b.Loads {
				served = append(served, m.Module+"="+BundlePath(m.Module, b.Name)+"/"+load)
			}
			restartOn = append(restartOn, m.Module+"."+BundleID(b.Name))
		}
	}
	sort.Strings(served)
	restartOn = append(restartOn, RuntimeModule+"."+NeedID("broker"))
	sort.Strings(restartOn)

	env := map[string]string{
		RuntimeToolModules: strings.Join(served, ","),
		RuntimeBrokerFile:  credential.Path,
	}
	process := map[string]any{
		"id": RuntimeModule + "." + RuntimeProcessID(), "type": "process", "name": RuntimeModule,
		"source": bundle.Source, "digest": bundle.Digest,
		"run":        []any{interpreter, bundle.Entrypoints[0]},
		"env":        env,
		"restart-on": toAny(restartOn),
	}
	if r.Account != "" {
		env[RuntimeOperatorAccount] = r.Account
		env[RuntimeOperatorHome] = accountHomeOf(r.Account, r.AccountHome)
		process["user"] = r.Account
	}
	// Routed through the artifact store as this network reaches it now, like everything the mesh
	// built; refused with the same words when there is no store to route through.
	if err := artifactsInto(process, RuntimeModule, with); err != nil {
		return nil, err
	}
	return process, nil
}

func toAny(in []string) []any {
	out := make([]any, 0, len(in))
	for _, s := range in {
		out = append(out, s)
	}
	return out
}

// RuntimeImageModule and RuntimeImageArtifact name the image every per-module tool container was
// built on: the tool runtime's own runtime image. With the runtime a module of its own, that image
// stays the way a module's SERVICE may be built and stops being the way tools reach a node (ADR 0175).
const (
	RuntimeImageModule   = "mesh-tools"
	RuntimeImageArtifact = "runtime"
)

// ToolContainerOnTheRuntime says why a manifest is the pattern ADR 0175 retires — a module whose tools
// are served from a container built on the tool runtime's image — or nothing when it is not. Judged
// from the manifest's own `build.on` when it is a repository manifest, and from what its build stood
// on when it is a built one, because a resolved manifest carries no build. The gate itself is
// registration's (to-be 38 WP2.4): once the runtime module is in the catalogue, this is refused.
//
// Three things must hold, and each alone is fine: declaring tools (a bundle does that); a container
// (a module's service may well be one); building on the runtime's image (a service written against
// the SDK may). All three is a container whose purpose is tools, which the runtime now serves.
func ToolContainerOnTheRuntime(m Manifest, against []string) string {
	if len(m.Tools) == 0 {
		return ""
	}
	container := false
	for _, r := range m.Resources {
		if fmt.Sprint(r["type"]) == "container" {
			container = true
		}
	}
	if !container {
		return ""
	}
	onTheRuntime := false
	if m.Build != nil {
		for _, on := range m.Build.On {
			if on.Module == RuntimeImageModule && on.Artifact == RuntimeImageArtifact {
				onTheRuntime = true
			}
		}
	}
	for _, ref := range against {
		path, kept := InArtifactStore(Recorded(ref))
		if kept && strings.HasPrefix(path, RuntimeImageModule+"/"+RuntimeImageArtifact+"@") {
			onTheRuntime = true
		}
	}
	if !onTheRuntime {
		return ""
	}
	return fmt.Sprintf(
		"%s declares tools and a container built on %s's %s image — a container whose purpose is "+
			"serving tools. The node's tool runtime (%s) serves every module's tools from its bundle "+
			"now (novox/hq ADR 0175, to-be 38); declare the tools as a bundle and drop the container",
		m.Module, RuntimeImageModule, RuntimeImageArtifact, RuntimeModule)
}