/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

import {ReferenceSymbol, ShimLocation, Symbol, SymbolKind, VariableSymbol} from '@angular/compiler-cli/src/ngtsc/typecheck/api';
import * as ts from 'typescript';


// Reverse mappings of enum would generate strings
export const ALIAS_NAME = ts.SymbolDisplayPartKind[ts.SymbolDisplayPartKind.aliasName];
export const SYMBOL_INTERFACE = ts.SymbolDisplayPartKind[ts.SymbolDisplayPartKind.interfaceName];
export const SYMBOL_PUNC = ts.SymbolDisplayPartKind[ts.SymbolDisplayPartKind.punctuation];
export const SYMBOL_SPACE = ts.SymbolDisplayPartKind[ts.SymbolDisplayPartKind.space];
export const SYMBOL_TEXT = ts.SymbolDisplayPartKind[ts.SymbolDisplayPartKind.text];


/**
 * Label for various kinds of Angular entities for TS display info.
 */
export enum DisplayInfoKind {
  COMPONENT = 'component',
  DIRECTIVE = 'directive',
  EVENT = 'event',
  REFERENCE = 'reference',
  ELEMENT = 'element',
  VARIABLE = 'variable',
  PIPE = 'pipe',
  PROPERTY = 'property',
  METHOD = 'method',
  TEMPLATE = 'template',
}

export interface DisplayInfo {
  kind: DisplayInfoKind;
  displayParts: ts.SymbolDisplayPart[];
  documentation: ts.SymbolDisplayPart[]|undefined;
}

export function getDisplayInfo(
    tsLS: ts.LanguageService, typeChecker: ts.TypeChecker,
    symbol: ReferenceSymbol|VariableSymbol): DisplayInfo {
  let kind: DisplayInfoKind;
  if (symbol.kind === SymbolKind.Reference) {
    kind = DisplayInfoKind.REFERENCE;
  } else if (symbol.kind === SymbolKind.Variable) {
    kind = DisplayInfoKind.VARIABLE;
  } else {
    throw new Error(
        `AssertionError: unexpected symbol kind ${SymbolKind[(symbol as Symbol).kind]}`);
  }

  const displayParts = createDisplayParts(
      symbol.declaration.name, kind, /* containerName */ undefined,
      typeChecker.typeToString(symbol.tsType));
  const documentation = getDocumentationFromTypeDefAtLocation(tsLS, symbol.shimLocation);
  return {
    kind,
    displayParts,
    documentation,
  };
}

/**
 * Construct a compound `ts.SymbolDisplayPart[]` which incorporates the container and type of a
 * target declaration.
 * @param name Name of the target
 * @param kind component, directive, pipe, etc.
 * @param containerName either the Symbol's container or the NgModule that contains the directive
 * @param type user-friendly name of the type
 * @param documentation docstring or comment
 */
export function createDisplayParts(
    name: string, kind: DisplayInfoKind, containerName: string|undefined,
    type: string|undefined): ts.SymbolDisplayPart[] {
  const containerDisplayParts = containerName !== undefined ?
      [
        {text: containerName, kind: SYMBOL_INTERFACE},
        {text: '.', kind: SYMBOL_PUNC},
      ] :
      [];

  const typeDisplayParts = type !== undefined ?
      [
        {text: ':', kind: SYMBOL_PUNC},
        {text: ' ', kind: SYMBOL_SPACE},
        {text: type, kind: SYMBOL_INTERFACE},
      ] :
      [];
  return [
    {text: '(', kind: SYMBOL_PUNC},
    {text: kind, kind: SYMBOL_TEXT},
    {text: ')', kind: SYMBOL_PUNC},
    {text: ' ', kind: SYMBOL_SPACE},
    ...containerDisplayParts,
    {text: name, kind: SYMBOL_INTERFACE},
    ...typeDisplayParts,
  ];
}

/**
 * Convert a `SymbolDisplayInfoKind` to a `ts.ScriptElementKind` type, allowing it to pass through
 * TypeScript APIs.
 *
 * In practice, this is an "illegal" type cast. Since `ts.ScriptElementKind` is a string, this is
 * safe to do if TypeScript only uses the value in a string context. Consumers of this conversion
 * function are responsible for ensuring this is the case.
 */
export function unsafeCastDisplayInfoKindToScriptElementKind(kind: DisplayInfoKind):
    ts.ScriptElementKind {
  return kind as string as ts.ScriptElementKind;
}

function getDocumentationFromTypeDefAtLocation(
    tsLS: ts.LanguageService, shimLocation: ShimLocation): ts.SymbolDisplayPart[]|undefined {
  const typeDefs =
      tsLS.getTypeDefinitionAtPosition(shimLocation.shimPath, shimLocation.positionInShimFile);
  if (typeDefs === undefined || typeDefs.length === 0) {
    return undefined;
  }
  return tsLS.getQuickInfoAtPosition(typeDefs[0].fileName, typeDefs[0].textSpan.start)
      ?.documentation;
}