import { executionPlanDigestAsync, type ExecutionPlan, hexDigest, hexDigestAsync, ExecutionPlanError } from "./plan.js";
import { portableReflectionValue } from "./reflection.js";
import type {
  BoundDependency,
  DependencyBinding,
  PackageExport,
  PersistentAttachment,
} from "../capability-model/types.js";
import { type ExecutionInstallation, type ExecutionGroupIdentity } from "./installation.js";

export interface ExecutionEnvironment {
  /** Explicit host placement. Merely including an optional module does not select it. */
  readonly placement: "service" | "module";
  /** Exact host executable/isolation inputs, computed by the trusted installer. */
  readonly hostDigest: string;
  readonly policyDigest: string;
  /** Identifier of the secret/config generation; never secret material. */
  readonly credentialGeneration: string;
}
export interface InstalledExecutionGroup extends ExecutionGroupIdentity {
  readonly packageRevision: string;
  readonly consumedPackages: readonly string[];
}
/** Conservative outbound closure. Runtime graph values, reverse callers, source
 * provenance and the workspace epoch are deliberately absent from this identity. */
export async function compileExecutionGroups(
  plan: ExecutionPlan,
  installation: ExecutionInstallation,
  environments: Readonly<Record<string, ExecutionEnvironment>>,
): Promise<InstalledExecutionGroup[]> {
  if (installation.plan !== plan.digest || (await executionPlanDigestAsync(plan)) !== plan.digest)
    throw new ExecutionPlanError("GROUP_PLAN_MISMATCH", plan.digest, "Expected one checked installation");
  const workspace = plan.definition.workspace;
  const packages = new Map(workspace.packageImports.map((p) => [p.revisionId as string, p]));
  const operations = new Map(plan.definition.operations.map((op) => [op.key, op]));
  const attachments = new Map<string, PersistentAttachment>(
    [...workspace.sharedAttachments, ...workspace.conformances.flatMap((c) => c.privateAttachments)].map((a) => [
      a.id,
      a,
    ]),
  );
  const logical = (revision: string) => {
    const pkg = packages.get(revision);
    if (!pkg) throw new ExecutionPlanError("GROUP_PACKAGE_MISSING", revision, "Uninstalled consumed package");
    return pkg.packageId;
  };
  const environment = (revision: string) => {
    const value = environments[revision];
    if (
      !value ||
      !["service", "module"].includes(value.placement) ||
      !/^[0-9a-f]{64}$/.test(value.hostDigest) ||
      !/^[0-9a-f]{64}$/.test(value.policyDigest) ||
      !value.credentialGeneration ||
      value.credentialGeneration.length > 4096
    )
      throw new ExecutionPlanError(
        "GROUP_ENVIRONMENT_MISSING",
        revision,
        "Expected checked host/policy digests and a credential generation",
      );
    return value;
  };
  const implementations = new Map(
    installation.packages.map((pkg) => {
      if (!pkg.service && !pkg.module) return [pkg.revision, undefined] as const;
      const implementation = pkg[environment(pkg.revision).placement];
      if (!implementation)
        throw new ExecutionPlanError(
          "GROUP_IMPLEMENTATION_MISSING",
          pkg.revision,
          "Host selected an unavailable implementation",
        );
      return [pkg.revision, implementation] as const;
    }),
  );
  const attachmentContract = (value: PersistentAttachment) => {
    const { displayName: _name, ...rest } = value;
    return value.kind === "state"
      ? rest
      : { ...rest, endpoints: value.endpoints.map(({ displayName: _name, ...endpoint }) => endpoint) };
  };
  const bindingContract = (value: DependencyBinding) =>
    value.kind === "query" ? { ...value, packageRevisionId: logical(value.packageRevisionId) } : value;
  const groups: InstalledExecutionGroup[] = [];
  for (const root of installation.packages.filter((p) => !!implementations.get(p.revision))) {
    const consumed = new Map<string, unknown>(),
      visited = new Set<string>(),
      visitedQueries = new Set<string>(),
      consumedPackages = new Set<string>();
    const remember = (key: string, value: unknown) => consumed.set(key, value);
    const storage = (id: string) => {
      const value = attachments.get(id);
      if (!value) throw new ExecutionPlanError("GROUP_STORAGE_MISSING", id, "Uninstalled consumed storage");
      remember(`storage:${id}`, attachmentContract(value));
    };
    // Deletion may visit related objects and their owned state. Conservatively
    // include the connected schema component, including possible future edges.
    const lifecycle = (atom: string) => {
      const visited = new Set<string>(),
        pending = [atom];
      const atoms = (constraint: Extract<PersistentAttachment, { kind: "edge" }>["endpoints"][number]["constraint"]) =>
        constraint.kind === "atom"
          ? [constraint.atomId as string]
          : workspace.conformances
              .filter((c) => c.interfaceRevisionId === constraint.interfaceRevisionId)
              .map((c) => c.atomId as string);
      while (pending.length) {
        const current = pending.pop()!;
        if (visited.has(current)) continue;
        visited.add(current);
        for (const owner of workspace.conformances.filter((c) => c.atomId === current))
          for (const attachment of owner.privateAttachments) storage(attachment.id);
        for (const attachment of attachments.values())
          if (attachment.kind === "edge" && attachment.endpoints.some((e) => atoms(e.constraint).includes(current))) {
            storage(attachment.id);
            pending.push(...attachment.endpoints.flatMap((e) => atoms(e.constraint)));
          }
      }
    };
    const targets = (binding: DependencyBinding, atom: string): string[] => {
      if (binding.kind === "interface" && binding.receiver === "input")
        return workspace.conformances
          .filter((c) => c.interfaceRevisionId === binding.interfaceRevisionId)
          .map((c) => c.atomId);
      if (!("via" in binding) || !binding.via) return [atom];
      storage(binding.via.edgeTypeId);
      const edge = attachments.get(binding.via.edgeTypeId);
      if (!edge || edge.kind !== "edge")
        throw new ExecutionPlanError("GROUP_EDGE_MISSING", atom, "Missing traversal edge");
      const endpoint = edge.endpoints.find((e) => e.projectionId !== binding.via!.projectionId)!;
      const constraint = endpoint.constraint;
      return constraint.kind === "atom"
        ? [constraint.atomId]
        : workspace.conformances
            .filter((c) => c.interfaceRevisionId === constraint.interfaceRevisionId)
            .map((c) => c.atomId);
    };
    const query = (revision: string, id: string) => {
      const key = JSON.stringify([revision, id]);
      if (visitedQueries.has(key)) return;
      visitedQueries.add(key);
      const value = plan.definition.queries.find((q) => q.id === key);
      if (!value) throw new ExecutionPlanError("GROUP_QUERY_MISSING", key, "Missing consumed query");
      remember(`query:${JSON.stringify([logical(revision), id])}`, value.query.checked.definitionDigest);
      for (const operation of value.operations) visit(operation);
    };
    const dependencies = (entry: PackageExport, bindings: readonly BoundDependency[], atom: string) => {
      for (const bound of bindings) {
        const target = bound.binding,
          port = entry.dependencyPorts.find((p) => p.id === bound.portId)!;
        if ("via" in target && target.via) storage(target.via.edgeTypeId);
        if (target.kind === "reflection") {
          for (const selector of target.selectors)
            remember("reflection:" + selector, portableReflectionValue(workspace, selector));
        } else if (target.kind === "state") storage(target.slotId);
        else if (target.kind === "edge") storage(target.edgeTypeId);
        else if (target.kind === "query") query(target.packageRevisionId, target.queryId);
        else if (target.kind === "interface" && port.requirement.kind === "interface") {
          const iface = workspace.interfaceImports.find((i) => i.revisionId === target.interfaceRevisionId)!;
          for (const targetAtom of targets(target, atom))
            for (const op of port.requirement.operations ?? iface.members.flatMap((m) => m.operations.map((o) => o.id)))
              visit(JSON.stringify([targetAtom, target.interfaceRevisionId, op]));
        } else if (target.kind === "creation") {
          for (const seed of target.owners) {
            const owner = workspace.conformances.find(
              (c) => c.atomId === target.atomId && c.interfaceRevisionId === seed.interfaceRevisionId,
            )!;
            remember(`birth:${owner.id}`, {
              id: owner.id,
              atom: owner.atomId,
              interface: owner.interfaceRevisionId,
              initialization: owner.initialization ?? [],
            });
            for (const attachment of owner.privateAttachments) storage(attachment.id);
          }
        } else
          throw new ExecutionPlanError(
            "GROUP_DEPENDENCY_UNSUPPORTED",
            bound.portId,
            "Cannot establish execution reuse for this dependency",
          );
      }
    };
    const visit = (key: string) => {
      if (visited.has(key)) return;
      visited.add(key);
      const operation = operations.get(key);
      if (!operation) throw new ExecutionPlanError("GROUP_OPERATION_MISSING", key, "Missing consumed operation");
      const binding = operation.binding;
      if (binding.kind === "package") {
        const pkg = packages.get(binding.packageRevisionId)!;
        const implementation = implementations.get(pkg.revisionId);
        if (!implementation)
          throw new ExecutionPlanError(
            "GROUP_IMPLEMENTATION_MISSING",
            pkg.revisionId,
            "Consumed package has no selected server implementation",
          );
        consumedPackages.add(pkg.packageId);
        remember(`implementation:${pkg.packageId}`, {
          digest: implementation.contentDigest,
          environment: environment(pkg.revisionId),
        });
        const entry = pkg.exports.find((e) => e.id === binding.exportId)!;
        const bindings = binding.dependencies.map((d) => ({ portId: d.portId, binding: bindingContract(d.binding) }));
        const acceptance = (binding.acceptanceDependencies ?? []).map((d) => ({
          portId: d.portId,
          binding: bindingContract(d.binding),
        }));
        const contract = {
          input: operation.input,
          output: operation.output,
          execution: operation.execution,
          scope: operation.scope,
          binding: {
            package: pkg.packageId,
            export: binding.exportId,
            dependencies: bindings,
            acceptanceDependencies: acceptance,
          },
        };
        // Deduplicate aliases of the same bound export, rather than keying its owner by reverse callers.
        remember(`binding:${hexDigest(contract)}`, contract);
        dependencies(entry, binding.dependencies, operation.atomId);
        if (entry.acceptanceExportId)
          dependencies(
            pkg.exports.find((e) => e.id === entry.acceptanceExportId)!,
            binding.acceptanceDependencies ?? [],
            operation.atomId,
          );
      } else {
        remember(`operation:${key}`, operation);
        if (binding.kind === "state") storage(binding.slotId);
        if (binding.kind === "edge") storage(binding.edgeTypeId);
        if (binding.kind === "lifecycle") lifecycle(operation.atomId);
      }
    };
    for (const operation of plan.definition.operations)
      if (operation.binding.kind === "package" && operation.binding.packageRevisionId === root.revision)
        visit(operation.key);
    const own = implementations.get(root.revision)!;
    const exports = packages.get(root.revision)!.exports.map(({ displayName: _name, dependencyPorts, ...entry }) => ({
      ...entry,
      dependencyPorts: dependencyPorts.map(({ displayName: _name, ...port }) => port),
    }));
    const entries = [...consumed].sort(([a], [b]) => (a < b ? -1 : a > b ? 1 : 0));
    groups.push({
      logicalId: logical(root.revision),
      packageRevision: root.revision,
      executionDigest: `sha256:${await hexDigestAsync({ implementation: own.contentDigest, exports, environment: environment(root.revision), versions: plan.definition.versions, consumed: entries })}`,
      consumedPackages: [...consumedPackages].sort(),
    });
  }
  return groups;
}