import { capabilityId, type InterfaceRevision, type InterfaceRevisionId } from "../capability-model/types.js";
import {
  TypeSubstitution,
  bindTypeParameters,
  type ClosedTypeArgument,
  type GenericTypeEnvironment,
} from "../capability-model/generics.js";
import { GenericSourceTypes } from "../capability-language/generic-types.js";
import { compileQuery } from "./compile.js";
import { QueryCompileError, type QueryDeclaration, type QueryTemplate } from "./types.js";

export function specializeQueryTemplate(
  template: QueryTemplate,
  arguments_: ClosedTypeArgument[],
  environment: GenericTypeEnvironment,
  interfaces: () => readonly InterfaceRevision[],
  identity: { id: string; displayName: string },
): QueryDeclaration {
  const obligations: NonNullable<QueryDeclaration["argumentRequirements"]> = [];
  const checked = {
    ...environment,
    implementsInterface: (
      target: Parameters<GenericTypeEnvironment["implementsInterface"]>[0],
      required: InterfaceRevisionId,
    ) => {
      obligations.push({ target, required });
      return environment.implementsInterface(target, required);
    },
  };
  const substitution = new TypeSubstitution({
    ...checked,
    arguments: bindTypeParameters(template.parameters, arguments_, checked, template.declaration.displayName),
  });
  return {
    ...structuredClone(template.declaration),
    ...identity,
    root: { kind: template.root.kind, interface: substitution.application(template.root.interface) },
    views: template.views
      .map((view) => {
        const target = substitution.object(view.target);
        const interfaceRevisionId = substitution.application(view.interface);
        if (target.kind === "interface") {
          if (target.interfaceRevisionId !== interfaceRevisionId)
            throw new QueryCompileError(
              "QUERY_VIEW_REQUIRED",
              "An interface argument must use its exact selected query view",
            );
          return undefined;
        }
        return { atomId: target.atomId, interfaceRevisionId };
      })
      .filter((view): view is NonNullable<typeof view> => !!view),
    allowances: template.allowances.map((allowance) => {
      const interfaceRevisionId = substitution.application(allowance.interface);
      const member = interfaces()
        .find((entry) => entry.revisionId === interfaceRevisionId)
        ?.members.find((entry) => entry.displayName === allowance.memberName);
      if (!member) throw new QueryCompileError("QUERY_ALLOWANCE", `Unknown template field ${allowance.memberName}`);
      return { interfaceRevisionId, memberId: member.id, uses: allowance.uses, reason: allowance.reason };
    }),
    application: { templateId: template.declaration.id, arguments: structuredClone(arguments_) },
    argumentRequirements: obligations,
  };
}

/** Check a document with only its declared bounds available, even if no concrete
 * specialization is installed. No concrete atom fields can leak into this check. */
export async function checkQueryTemplate(
  template: QueryTemplate,
  interfaces: readonly InterfaceRevision[],
  read: (name: string) => Promise<string>,
) {
  const types = new GenericSourceTypes(new Map());
  for (const contract of interfaces) types.register(contract.displayName, contract);
  const arguments_: ClosedTypeArgument[] = template.parameters.map((parameter) => {
    if (parameter.kind !== "object")
      throw new QueryCompileError(
        "QUERY_TEMPLATE_PARAMETER",
        "Query templates currently require object parameters with explicit interface views; scalar/value polymorphism is not queryable",
      );
    return {
      kind: "object",
      target: { kind: "atom", atomId: capabilityId.atom(`query-bound:${template.declaration.id}:${parameter.id}`) },
    };
  });
  const bindings = new Map(template.parameters.map((parameter, index) => [parameter.id, arguments_[index]!]));
  const substitution = new TypeSubstitution({ ...types.environment(), arguments: bindings });
  const evidence = new Map(
    arguments_.map((argument, index) => {
      const parameter = template.parameters[index]!;
      const target = argument.kind === "object" && argument.target.kind === "atom" ? argument.target.atomId : "";
      return [
        target,
        new Set(
          parameter.kind === "object" ? parameter.implements.map((bound) => substitution.application(bound)) : [],
        ),
      ];
    }),
  );
  const implies = (offered: string, required: string, seen = new Set<string>()): boolean => {
    if (offered === required) return true;
    if (seen.has(offered)) return false;
    seen.add(offered);
    const contract = types.definitions.get(offered);
    return (contract?.requiredInterfaces ?? []).some((parent) => implies(parent, required, seen));
  };
  const environment = {
    ...types.environment(),
    implementsInterface: (
      target: Parameters<GenericTypeEnvironment["implementsInterface"]>[0],
      required: InterfaceRevisionId,
    ) =>
      target.kind === "atom" && [...(evidence.get(target.atomId) ?? [])].some((offered) => implies(offered, required)),
  };
  const declaration = specializeQueryTemplate(
    template,
    arguments_,
    environment,
    () => [...types.definitions.values()],
    template.declaration,
  );
  for (const view of declaration.views)
    if (!environment.implementsInterface({ kind: "atom", atomId: view.atomId }, view.interfaceRevisionId))
      throw new QueryCompileError(
        "QUERY_TEMPLATE_BOUND",
        `The declared bounds do not guarantee the selected view ${view.interfaceRevisionId}`,
      );
  for (const application of types.applications.values())
    for (const obligation of application.argumentRequirements ?? [])
      if (!environment.implementsInterface(obligation.target, obligation.required))
        throw new QueryCompileError(
          "QUERY_TEMPLATE_BOUND",
          `Template arguments do not guarantee ${obligation.required}`,
        );
  return compileQuery(declaration, [...types.definitions.values()], read);
}