import * as t from "@babel/types";
import {
  unwrapJavaScriptExpression,
  semanticStaticPropertyKey,
  semanticFinalObjectProperty,
  semanticFinalObjectStringProperty,
} from "./javascriptAstValues.js";
import { range } from "./javascriptStaticAnalysisHelpers.js";
import type { JavaScriptSemanticReference } from "./javascriptSemanticIr.js";
import {
  resolveSemanticBindingState,
  semanticStableInitializer,
  type JavaScriptSemanticAnalysisState,
  type JavaScriptBindingIndex,
} from "./javascriptSemanticState.js";
import type {
  JavaScriptRpcEndpoint,
  JavaScriptRpcScan,
} from "./javascriptRpcEndpoints.js";

/**
 * Find source-body string values owned by a GraphQL Source-shaped literal.
 * A later duplicate or spread can make the effective `body` unknown, but the
 * earlier strings still belong to this object and must not become standalone
 * operation findings during the string scan.
 */
const graphqlSourceBodyLiterals = (
  node: t.ObjectExpression,
): readonly t.StringLiteral[] | undefined => {
  const hasLocationOffset = node.properties.some(
    (property) =>
      t.isObjectProperty(property) &&
      semanticStaticPropertyKey(property.key, property.computed) ===
        "locationOffset",
  );
  if (!hasLocationOffset) return undefined;

  const bodyStrings = (object: t.ObjectExpression) =>
    object.properties.flatMap((property) =>
      t.isObjectProperty(property) &&
      semanticStaticPropertyKey(property.key, property.computed) === "body" &&
      t.isStringLiteral(property.value)
        ? [property.value]
        : [],
    );
  const bodies = bodyStrings(node);

  // Inline object spreads can own additional body values which the surrounding
  // Source object may select. Include only body-key string literals from those
  // spread values; ordinary strings elsewhere in the object remain scannable.
  const visited = new WeakSet<t.ObjectExpression>();
  visited.add(node);
  const pending = node.properties.flatMap((property) => {
    if (!t.isSpreadElement(property)) return [];
    const spread = unwrapJavaScriptExpression(property.argument).node;
    return t.isObjectExpression(spread) ? [spread] : [];
  });
  while (pending.length > 0) {
    const current = pending.pop();
    if (current === undefined || visited.has(current)) continue;
    visited.add(current);
    bodies.push(...bodyStrings(current));
    for (const property of current.properties) {
      if (t.isSpreadElement(property)) {
        const spread = unwrapJavaScriptExpression(property.argument).node;
        if (t.isObjectExpression(spread)) pending.push(spread);
      }
    }
  }
  return bodies.length === 0 ? undefined : bodies;
};

const GRAPHQL_OPERATION_TYPES: ReadonlySet<string> = new Set([
  "query",
  "mutation",
  "subscription",
]);

// GraphQL October 2021 §2.1.7: ignored BOM, tab/space, line endings, commas;
// comments are consumed separately below.
const isGraphqlIgnoredCharacter = (character: string): boolean =>
  character === "," ||
  character === "\uFEFF" ||
  character === "\t" ||
  character === " " ||
  character === "\n" ||
  character === "\r";

/** Return the first offset after GraphQL ignored tokens. */
const skipGraphqlIgnored = (text: string, start: number): number => {
  const limit = text.length;
  let index = start;
  while (index < limit) {
    const character = text.charAt(index);
    if (isGraphqlIgnoredCharacter(character)) index += 1;
    else if (character === "#") {
      while (index < limit && !/[\n\r]/u.test(text.charAt(index))) index += 1;
    } else break;
  }
  return index;
};

const graphqlNameAt = (
  text: string,
  index: number,
): { readonly value: string; readonly end: number } | undefined => {
  const name = /^[_A-Za-z][_0-9A-Za-z]*/u.exec(text.slice(index))?.[0];
  return name === undefined
    ? undefined
    : { value: name, end: index + name.length };
};

/** Recover a named operation from GraphQL document text. */
const graphqlOperationFromText = (
  text: string,
): JavaScriptRpcEndpoint | undefined => {
  const type = graphqlNameAt(text, skipGraphqlIgnored(text, 0));
  if (type === undefined || !GRAPHQL_OPERATION_TYPES.has(type.value))
    return undefined;
  const name = graphqlNameAt(text, skipGraphqlIgnored(text, type.end));
  if (name === undefined) return undefined;
  const index = skipGraphqlIgnored(text, name.end);
  const next = text.charAt(index);
  // Keep the existing bounded recognition scope: a named operation followed
  // by variable definitions, a directive, or a selection set with a field.
  const hasHeader =
    next === "("
      ? text.charAt(skipGraphqlIgnored(text, index + 1)) === "$"
      : (next === "@" || next === "{") &&
        graphqlNameAt(text, skipGraphqlIgnored(text, index + 1)) !== undefined;
  return hasHeader
    ? { value: name.value, mechanism: `graphql:${type.value}` }
    : undefined;
};

/** Recover a named operation from a precompiled GraphQL document object. */
const graphqlOperationFromDocumentNode = (
  node: t.ObjectExpression,
): JavaScriptRpcEndpoint | undefined => {
  if (semanticFinalObjectStringProperty(node, "kind") !== "OperationDefinition")
    return undefined;
  const type = semanticFinalObjectStringProperty(node, "operation");
  if (type === undefined || !GRAPHQL_OPERATION_TYPES.has(type))
    return undefined;
  const name = semanticFinalObjectProperty(node, "name");
  if (
    !t.isObjectExpression(name) ||
    semanticFinalObjectStringProperty(name, "kind") !== "Name"
  )
    return undefined;
  const value = semanticFinalObjectStringProperty(name, "value");
  return value === undefined
    ? undefined
    : { value, mechanism: `graphql:${type}` };
};

interface GraphqlSourceDependency {
  readonly bindingId: string;
  readonly name: string;
  readonly location?: JavaScriptSemanticReference["location"];
}

interface GraphqlSourceCopy {
  readonly source: t.ObjectExpression;
  readonly dependencies: readonly GraphqlSourceDependency[];
  readonly operations: readonly JavaScriptRpcEndpoint[];
}

/** One private constant owns its initializer; exported or projected values do not. */
const graphqlPrivateBinding = (
  node: t.Identifier,
  state: JavaScriptSemanticAnalysisState,
  sourceType: t.Program["sourceType"],
) => {
  const binding = resolveSemanticBindingState(state, node, node.name);
  if (binding === undefined || binding.mutable) return undefined;
  const scope = state.scopesById.get(binding.scopeId);
  if (
    scope === undefined ||
    (scope.kind === "program" && sourceType !== "module")
  )
    return undefined;
  const initializer = semanticStableInitializer(binding, state);
  if (initializer?.projection.length !== 0) return undefined;
  const declaration = state.parentsByNode.get(initializer.node);
  const statement = t.isVariableDeclarator(declaration)
    ? state.parentsByNode.get(declaration)
    : undefined;
  return t.isVariableDeclaration(statement) &&
    !t.isExportNamedDeclaration(state.parentsByNode.get(statement))
    ? { binding, initializer }
    : undefined;
};

/** Resolve potential metadata ownership; references must still prove exclusivity. */
const graphqlSourceObjectValue = (
  node: t.Node | undefined,
  index: JavaScriptBindingIndex,
  dependencies: GraphqlSourceDependency[],
): t.ObjectExpression | undefined => {
  if (node === undefined) return undefined;
  const state = index.bindings;
  const visited = new Set<t.Node>();
  while (node !== undefined && !visited.has(node)) {
    visited.add(node);
    node = unwrapJavaScriptExpression(node).node;
    if (t.isObjectExpression(node)) return node;
    if (!t.isIdentifier(node)) return undefined;
    const owner = graphqlPrivateBinding(node, state, index.sourceType);
    if (owner === undefined) return undefined;
    const { binding, initializer } = owner;
    if (
      initializer.node.end == null ||
      node.start == null ||
      node.loc == null ||
      initializer.node.end > node.start
    )
      return undefined;
    dependencies.push({
      bindingId: binding.bindingId,
      name: binding.name,
      location: range(node),
    });
    node = initializer.node;
  }
  return undefined;
};

const graphqlDocumentSource = (
  node: t.ObjectExpression,
  index: JavaScriptBindingIndex,
): Omit<GraphqlSourceCopy, "operations"> | undefined => {
  const dependencies: GraphqlSourceDependency[] = [];
  const loc = graphqlSourceObjectValue(
    semanticFinalObjectProperty(node, "loc"),
    index,
    dependencies,
  );
  const source =
    loc === undefined
      ? undefined
      : graphqlSourceObjectValue(
          semanticFinalObjectProperty(loc, "source"),
          index,
          dependencies,
        );
  return source !== undefined &&
    graphqlContainerOwnership(node, index, dependencies)
    ? { source, dependencies }
    : undefined;
};

/** Follow containment to the binding that can expose or mutate this document. */
const graphqlContainerOwnership = (
  document: t.ObjectExpression,
  index: JavaScriptBindingIndex,
  dependencies: GraphqlSourceDependency[],
): boolean => {
  const state = index.bindings;
  let node: t.Node = document;
  for (;;) {
    const parent = state.parentsByNode.get(node);
    if (parent === undefined) return false;
    if (t.isObjectProperty(parent) && parent.value === node) {
      const object = state.parentsByNode.get(parent);
      if (!t.isObjectExpression(object)) return false;
      node = object;
    } else if (
      t.isArrayExpression(parent) ||
      unwrapJavaScriptExpression(parent).node === node
    )
      node = parent;
    else if (t.isExpressionStatement(parent)) return true;
    else if (t.isVariableDeclarator(parent) && parent.init === node) {
      if (!t.isIdentifier(parent.id)) return false;
      const owner = graphqlPrivateBinding(parent.id, state, index.sourceType);
      if (owner?.initializer.node !== node) return false;
      const { binding } = owner;
      dependencies.push({ bindingId: binding.bindingId, name: binding.name });
      return true;
    } else return false;
  }
};

const graphqlDocumentOperations = (
  node: t.ObjectExpression,
  operation: JavaScriptRpcEndpoint | undefined,
): readonly JavaScriptRpcEndpoint[] => {
  if (operation !== undefined) return [operation];
  if (semanticFinalObjectStringProperty(node, "kind") !== "Document") return [];
  const definitions = semanticFinalObjectProperty(node, "definitions");
  return t.isArrayExpression(definitions)
    ? definitions.elements.flatMap((definition) => {
        const recovered = t.isObjectExpression(definition)
          ? graphqlOperationFromDocumentNode(definition)
          : undefined;
        return recovered === undefined ? [] : [recovered];
      })
    : [];
};

const graphqlOperationKey = (operation: JavaScriptRpcEndpoint): string =>
  `${operation.mechanism}:${operation.value}`;

/** Any non-metadata use makes that connected alias component uncertain. */
interface GraphqlSourceReferenceIndex {
  readonly allowed: Map<string, Set<string>>;
  readonly neighbors: Map<string, Set<string>>;
  readonly byName: Map<string, Set<string>>;
}

function* graphqlSourceReferenceIndexSteps(
  copies: readonly GraphqlSourceCopy[],
): Generator<void, GraphqlSourceReferenceIndex> {
  const allowed = new Map<string, Set<string>>();
  const neighbors = new Map<string, Set<string>>();
  const byName = new Map<string, Set<string>>();
  let examined = 0;
  for (const { dependencies } of copies) {
    const first = dependencies[0]?.bindingId;
    for (const { bindingId, name, location } of dependencies) {
      if (++examined % 1024 === 0) yield;
      const sites = allowed.get(bindingId) ?? new Set<string>();
      if (location !== undefined) sites.add(JSON.stringify(location));
      allowed.set(bindingId, sites);
      const names = byName.get(name) ?? new Set<string>();
      names.add(bindingId);
      byName.set(name, names);
      if (first === undefined || first === bindingId) continue;
      const left = neighbors.get(first) ?? new Set<string>();
      const right = neighbors.get(bindingId) ?? new Set<string>();
      left.add(bindingId);
      right.add(first);
      neighbors.set(first, left);
      neighbors.set(bindingId, right);
    }
  }
  return { allowed, neighbors, byName };
}

function* uncertainGraphqlSourceBindingsSteps(
  index: GraphqlSourceReferenceIndex,
  references: readonly JavaScriptSemanticReference[],
): Generator<void, ReadonlySet<string>> {
  const { allowed, neighbors, byName } = index;
  const uncertain = new Set<string>();
  let examined = 0;
  for (const reference of references) {
    if (++examined % 1024 === 0) yield;
    // Direct eval may reach private lexical objects. Indirect eval cannot;
    // classic-script globals are already rejected at private-binding admission.
    if (reference.name === "eval") return new Set(allowed.keys());
    if (reference.bindingId !== null) {
      const sites = allowed.get(reference.bindingId);
      if (
        sites !== undefined &&
        (reference.role !== "read" ||
          !sites.has(JSON.stringify(reference.location)))
      )
        uncertain.add(reference.bindingId);
    } else if (
      reference.resolution === "unknown" ||
      reference.resolution === "ambiguous"
    )
      for (const bindingId of byName.get(reference.name) ?? [])
        uncertain.add(bindingId);
  }
  const pending = [...uncertain];
  for (
    let bindingId = pending.pop();
    bindingId !== undefined;
    bindingId = pending.pop()
  )
    for (const neighbor of neighbors.get(bindingId) ?? []) {
      if (++examined % 1024 === 0) yield;
      if (!uncertain.has(neighbor)) {
        uncertain.add(neighbor);
        pending.push(neighbor);
      }
    }
  return uncertain;
}

function* provenGraphqlSourceCopiesSteps(
  copies: readonly GraphqlSourceCopy[],
  references: readonly JavaScriptSemanticReference[],
): Generator<GraphqlSourceCopy | void, void> {
  const index = yield* graphqlSourceReferenceIndexSteps(copies);
  const uncertain = yield* uncertainGraphqlSourceBindingsSteps(
    index,
    references,
  );
  for (const copy of copies)
    yield copy.dependencies.every(({ bindingId }) => !uncertain.has(bindingId))
      ? copy
      : undefined;
}

const graphqlOperationFromTemplate = (
  node: t.TemplateLiteral,
): JavaScriptRpcEndpoint | undefined => {
  // Interpolations may contain fragment definitions. Continue only
  // across quasis that contain ignored tokens; prose or dynamic text
  // before an operation prevents claiming a later operation belongs to
  // this document prefix.
  for (const quasi of node.quasis) {
    const cooked = quasi.value.cooked;
    if (cooked === undefined || cooked === null) return undefined;
    if (skipGraphqlIgnored(cooked, 0) === cooked.length) continue;
    return graphqlOperationFromText(cooked);
  }
  return undefined;
};

export const createJavaScriptGraphqlScan = (
  index: JavaScriptBindingIndex,
): JavaScriptRpcScan => {
  const bodies = new WeakSet<t.Node>();
  const copied = new WeakMap<t.ObjectExpression, Set<string>>();
  const copies: GraphqlSourceCopy[] = [];
  const sources: {
    readonly source: t.ObjectExpression;
    readonly node: t.StringLiteral;
    readonly operation: JavaScriptRpcEndpoint;
  }[] = [];
  const retainCopy = ({ source, operations }: GraphqlSourceCopy) => {
    const keys = copied.get(source) ?? new Set<string>();
    for (const operation of operations)
      keys.add(graphqlOperationKey(operation));
    copied.set(source, keys);
  };
  return {
    inspect: (node: t.Node): JavaScriptRpcEndpoint | undefined => {
      if (t.isStringLiteral(node))
        return bodies.has(node)
          ? undefined
          : graphqlOperationFromText(node.value);
      if (t.isTemplateLiteral(node)) return graphqlOperationFromTemplate(node);
      if (!t.isObjectExpression(node)) return undefined;
      const operation = graphqlOperationFromDocumentNode(node);
      if (semanticFinalObjectProperty(node, "loc") !== undefined) {
        const operations = graphqlDocumentOperations(node, operation);
        const source =
          operations.length === 0
            ? undefined
            : graphqlDocumentSource(node, index);
        if (source !== undefined) {
          copies.push({ ...source, operations });
        }
      }
      const owned = graphqlSourceBodyLiterals(node);
      if (owned !== undefined) {
        for (const body of owned) bodies.add(body);
        const body = semanticFinalObjectProperty(node, "body");
        const recovered = t.isStringLiteral(body)
          ? graphqlOperationFromText(body.value)
          : undefined;
        if (t.isStringLiteral(body) && recovered !== undefined)
          sources.push({ source: node, node: body, operation: recovered });
      }
      return operation;
    },
    *finish() {
      if (sources.length > 0 && copies.length > 0) {
        const references = yield* index.referencesSteps();
        for (const copy of provenGraphqlSourceCopiesSteps(copies, references)) {
          if (copy !== undefined) retainCopy(copy);
          yield;
        }
      }
      for (const { source, node, operation } of sources)
        yield copied.get(source)?.has(graphqlOperationKey(operation))
          ? undefined
          : { node, ...operation };
      sources.length = 0;
      copies.length = 0;
    },
  };
};