import { createHash } from "node:crypto";
import {
  capabilityId,
  type PackageExport,
  type PackageExportId,
  type DependencyPort,
  type PackageRevision,
} from "./types.js";
import {
  TypeSubstitution,
  GenericTypeError,
  bindTypeParameters,
  canonicalTypeArgument,
  type TypeParameter,
  type ValueTypeExpression,
  type ObjectTypeExpression,
  type InterfaceApplicationExpression,
  type GenericTypeEnvironment,
  type ClosedTypeArgument,
  type ValueAliasDefinition,
} from "./generics.js";

export type GenericDependencyPort = Omit<DependencyPort, "requirement"> & {
  requirement:
    | {
        kind: "state";
        valueType: ValueTypeExpression;
        primitives: Extract<DependencyPort["requirement"], { kind: "state" }>["primitives"];
      }
    | {
        kind: "edge";
        target: ObjectTypeExpression;
        cardinality: Extract<DependencyPort["requirement"], { kind: "edge" }>["cardinality"];
        primitives: Extract<DependencyPort["requirement"], { kind: "edge" }>["primitives"];
      }
    | { kind: "interface"; application: InterfaceApplicationExpression }
    | { kind: "constructor"; target: ObjectTypeExpression; inputType: ValueTypeExpression };
};

export interface GenericPackageExport {
  id: PackageExportId;
  displayName: string;
  parameters: TypeParameter[];
  kind: "operation" | "function";
  inputType: ValueTypeExpression;
  outputType: ValueTypeExpression;
  eventType?: ValueTypeExpression;
  mode?: Extract<PackageExport, { kind: "operation" }>["mode"];
  receiverRequirement:
    | { kind: "any-object" }
    | { kind: "target"; target: ObjectTypeExpression }
    | { kind: "interfaces"; interfaces: InterfaceApplicationExpression[] };
  dependencyPorts: GenericDependencyPort[];
  aliases: ValueAliasDefinition[];
}

/** A closed manifest is a Nix build input, never a mutable source checkout. */
export const specializePackageExport = (
  pkg: PackageRevision,
  definition: GenericPackageExport,
  arguments_: ClosedTypeArgument[],
  environment: GenericTypeEnvironment,
): PackageExport => {
  const lexical = { ...environment, aliases: new Map(definition.aliases.map((alias) => [alias.id, alias])) };
  const bindings = bindTypeParameters(definition.parameters, arguments_, lexical, definition.displayName);
  const substitution = new TypeSubstitution({ ...lexical, arguments: bindings });
  const digest = createHash("sha256")
    .update(
      JSON.stringify([
        "quixos-package-specialization-v1",
        pkg.revisionId,
        [pkg.source.repository, pkg.source.commit],
        definition.id,
        arguments_.map(canonicalTypeArgument),
        environment.self ?? null,
      ]),
    )
    .digest("hex");
  const ports: DependencyPort[] = definition.dependencyPorts.map((port) => {
    const requirement = port.requirement;
    switch (requirement.kind) {
      case "state":
        return { ...port, requirement: { ...requirement, valueType: substitution.value(requirement.valueType) } };
      case "edge":
        return { ...port, requirement: { ...requirement, target: substitution.object(requirement.target) } };
      case "interface":
        return {
          ...port,
          requirement: { kind: "interface", interfaceRevisionId: substitution.application(requirement.application) },
        };
      case "constructor": {
        const target = substitution.object(requirement.target);
        if (target.kind !== "atom")
          throw new GenericTypeError(
            "constructor-target",
            port.displayName,
            "Constructor ports require a concrete atom argument, not an interface view",
          );
        return {
          ...port,
          requirement: {
            kind: "constructor",
            atomId: target.atomId,
            inputType: substitution.value(requirement.inputType),
          },
        };
      }
    }
  });
  const common = {
    id: capabilityId.packageExport(`export-application:sha256:${digest}`),
    displayName: `${definition.displayName}$${digest}`,
    inputType: substitution.value(definition.inputType),
    outputType: substitution.value(definition.outputType),
    dependencyPorts: ports,
    application: {
      exportId: definition.id,
      arguments: structuredClone(arguments_),
      ...(environment.self ? { self: environment.self } : {}),
    },
  };
  if (definition.kind === "function") return { ...common, kind: "function" };
  const receiver = definition.receiverRequirement;
  const target = receiver.kind === "target" ? substitution.object(receiver.target) : undefined;
  return {
    ...common,
    kind: "operation",
    mode: definition.mode!,
    ...(definition.eventType ? { eventType: substitution.value(definition.eventType) } : {}),
    receiverRequirement: target
      ? target.kind === "atom"
        ? { kind: "exact-atom", atomId: target.atomId }
        : { kind: "all-interfaces", interfaceRevisionIds: [target.interfaceRevisionId] }
      : receiver.kind === "interfaces"
        ? {
            kind: "all-interfaces",
            interfaceRevisionIds: receiver.interfaces.map((value) => substitution.application(value)),
          }
        : { kind: "any-object" },
  };
};