import type { GenericPackageExport, GenericDependencyPort } from "../capability-model/generic-packages.js";
import type { InterfaceRevision, ValueType } from "../capability-model/types.js";
import type {
  ValueTypeExpression,
  ObjectTypeExpression,
  TypeArgumentExpression,
  TypeParameter,
  ValueAliasDefinition,
} from "../capability-model/generics.js";

/** Universal source contracts. Only closed exports get executable codecs. */
export const genericImplementationType = (
  definition: GenericPackageExport,
  interfaces: InterfaceRevision[],
  concrete: (type: ValueType) => string,
): string => {
  const names = new Map(definition.parameters.map((parameter, index) => [parameter.id, `T${index}`]));
  type Scope = { arguments: Map<string, string>; aliases: ValueAliasDefinition[] };
  const rootScope = (): Scope => ({ arguments: new Map(), aliases: definition.aliases });
  const object = (entries: [string, string][]) =>
    `{${entries.map(([key, value]) => `${JSON.stringify(key)}:${value}`).join(";")}}`;
  const target = (type: ObjectTypeExpression, scope: Scope): string => {
    if (type.kind === "parameter") {
      const bound = scope.arguments.get(type.parameterId);
      if (bound) return bound;
      const name = names.get(type.parameterId);
      if (!name) throw new Error(`Unbound object parameter ${type.parameterId}`);
      return name;
    }
    if (type.kind === "atom") return JSON.stringify(`atom:${type.atomId}`);
    if (type.kind === "interface") return JSON.stringify(`interface:${type.interfaceRevisionId}`);
    if (type.kind === "application")
      return `QxApplied<${JSON.stringify(type.application.definitionId)}, [${type.application.arguments.map((arg) => argument(arg, scope)).join(",")}]>`;
    throw new Error("Generic package Self must be expressed as an explicit object parameter");
  };
  const argument = (arg: TypeArgumentExpression, scope: Scope): string =>
    arg.kind === "value" ? value(arg.type, scope) : target(arg.target, scope);
  const bind = (parameters: TypeParameter[], args: TypeArgumentExpression[], scope: Scope): Scope => {
    if (parameters.length !== args.length) throw new Error("Wrong generic arity during code generation");
    const result = new Map(scope.arguments);
    // Render arguments in their original lexical scope before introducing binders.
    const rendered = args.map((arg) => argument(arg, scope));
    parameters.forEach((parameter, index) => result.set(parameter.id, rendered[index]));
    return { ...scope, arguments: result };
  };
  const value = (type: ValueTypeExpression, scope: Scope, depth = 0): string => {
    if (depth > 128) throw new Error("Generic type expansion exceeds depth limit");
    switch (type.kind) {
      case "parameter": {
        const bound = scope.arguments.get(type.parameterId);
        if (bound) return bound;
        const name = names.get(type.parameterId);
        if (!name) throw new Error(`Unbound value parameter ${type.parameterId}`);
        return name;
      }
      case "object-ref":
        return `QxObjectRef<${target(type.expectation, scope)}>`;
      case "record":
        return object(Object.entries(type.fields).map(([name, field]) => [name, value(field, scope, depth + 1)]));
      case "optional":
        return `(${value(type.value, scope, depth + 1)} | null)`;
      case "list":
        return `Array<${value(type.value, scope, depth + 1)}>`;
      case "alias": {
        const alias = scope.aliases.find((entry) => entry.id === type.definitionId);
        if (!alias) throw new Error(`Missing alias ${type.definitionId}`);
        return value(alias.body, bind(alias.parameters, type.arguments, scope), depth + 1);
      }
      default:
        return concrete(type);
    }
  };
  const params = (type: ValueTypeExpression, scope: Scope) =>
    type.kind === "builtin" && type.name === "unit" ? "" : `input:${value(type, scope)}`;
  const port = (entry: GenericDependencyPort): string => {
    const requirement = entry.requirement,
      scope = rootScope();
    switch (requirement.kind) {
      case "state":
        return object([
          ...requirement.primitives.map((primitive): [string, string] => {
            if (primitive === "read") return ["get", `()=>Promise<${value(requirement.valueType, scope)}>`];
            if (primitive === "write") return ["set", `(value:${value(requirement.valueType, scope)})=>Promise<void>`];
            throw new Error(`Unsupported generic state primitive ${primitive}`);
          }),
          ...(requirement.primitives.includes("read")
            ? [["live", "()=>Promise<QxLiveValue>"] as [string, string]]
            : []),
        ]);
      case "edge": {
        const ref = `QxObjectRef<${target(requirement.target, scope)}>`;
        const methods = requirement.primitives.map((primitive): [string, string] => {
          if (primitive === "resolve") return ["resolve", `()=>Promise<Array<${ref}>>`];
          if (primitive === "connect" || primitive === "disconnect")
            return [primitive, `(target:${ref})=>Promise<void>`];
          throw new Error(`Unsupported generic edge primitive ${primitive}`);
        });
        if (requirement.primitives.includes("resolve"))
          methods.push(["collection", `()=>Promise<RelationshipCollection<${ref}>>`]);
        if (
          ["resolve", "connect", "disconnect"].every((primitive) =>
            requirement.primitives.includes(primitive as "resolve"),
          )
        )
          methods.push([
            "replace",
            `(entries:RelationshipEntry<${ref}>[],expectedRevision:bigint)=>Promise<RelationshipCollection<${ref}>>`,
          ]);
        return object(methods);
      }
      case "constructor":
        return object([
          [
            "construct",
            `(${params(requirement.inputType, scope)})=>Promise<QxObjectRef<${target(requirement.target, scope)}>>`,
          ],
        ]);
      case "interface": {
        const contract = interfaces.find((entry) => entry.revisionId === requirement.application.definitionId);
        if (!contract) throw new Error(`Missing generic port contract ${requirement.application.definitionId}`);
        const local = {
          ...bind(contract.template?.parameters ?? [], requirement.application.arguments, scope),
          aliases: contract.template?.aliases ?? [],
        };
        const operations = (contract.template?.members ?? contract.members).flatMap((member) =>
          member.operations
            .filter((op) => op.mode === "call" && op.scope !== "class")
            .map((op) => ({ ...op, name: `${member.displayName}.${op.displayName}` })),
        );
        return object([
          ["objectId", `QxObjectRef<${target({ kind: "application", application: requirement.application }, scope)}>`],
          ["live", object(operations.map((op) => [op.name, `(${params(op.inputType, local)})=>Promise<QxLiveValue>`]))],
          ...operations.map(
            (op) =>
              [op.name, `(${params(op.inputType, local)})=>Promise<${value(op.outputType, local)}>`] as [
                string,
                string,
              ],
          ),
        ]);
      }
    }
  };
  const declarations = definition.parameters
    .map((parameter) => `${names.get(parameter.id)}${parameter.kind === "object" ? " extends string" : ""}`)
    .join(",");
  const receiver = definition.receiverRequirement;
  const context = object([
    ...(definition.kind === "function"
      ? []
      : [
          [
            "objectId",
            `QxObjectRef<${receiver.kind === "target" ? target(receiver.target, rootScope()) : "string"}>`,
          ] as [string, string],
        ]),
    ["input", value(definition.inputType, rootScope())],
    ["ports", object(definition.dependencyPorts.map((entry) => [entry.displayName, port(entry)]))],
  ]);
  const contextWithLifecycle =
    definition.kind === "function"
      ? `${context} & {signal?: AbortSignal}`
      : `${context} & QxContextLifecycle<${context} & {signal?: AbortSignal}>`;
  const result = value(definition.eventType ?? definition.outputType, rootScope());
  const handler = `<${declarations}>(context:${contextWithLifecycle})=>${result}|Promise<${result}>`;
  const derived = `{kind:"derived";get:${handler}}`;
  return definition.eventType
    ? derived
    : `(${handler})${definition.kind === "operation" && definition.mode === "call" ? ` | ${derived}` : ""}`;
};