/**
 * @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 {AbstractEmitterVisitor, CATCH_ERROR_VAR, CATCH_STACK_VAR, EmitterVisitorContext, OutputEmitter} from './abstract_emitter';
import * as o from './output_ast';

export function debugOutputAstAsTypeScript(ast: o.Statement|o.Expression|o.Type|any[]): string {
  const converter = new _TsEmitterVisitor();
  const ctx = EmitterVisitorContext.createRoot();
  const asts: any[] = Array.isArray(ast) ? ast : [ast];

  asts.forEach((ast) => {
    if (ast instanceof o.Statement) {
      ast.visitStatement(converter, ctx);
    } else if (ast instanceof o.Expression) {
      ast.visitExpression(converter, ctx);
    } else if (ast instanceof o.Type) {
      ast.visitType(converter, ctx);
    } else {
      throw new Error(`Don't know how to print debug info for ${ast}`);
    }
  });
  return ctx.toSource();
}

export type ReferenceFilter = (reference: o.ExternalReference) => boolean;

export class TypeScriptEmitter implements OutputEmitter {
  emitStatementsAndContext(
      genFilePath: string, stmts: o.Statement[], preamble: string = '',
      emitSourceMaps: boolean = true, referenceFilter?: ReferenceFilter,
      importFilter?: ReferenceFilter): {sourceText: string, context: EmitterVisitorContext} {
    const converter = new _TsEmitterVisitor(referenceFilter, importFilter);

    const ctx = EmitterVisitorContext.createRoot();

    converter.visitAllStatements(stmts, ctx);

    const preambleLines = preamble ? preamble.split('\n') : [];
    converter.reexports.forEach((reexports, exportedModuleName) => {
      const reexportsCode =
          reexports.map(reexport => `${reexport.name} as ${reexport.as}`).join(',');
      preambleLines.push(`export {${reexportsCode}} from '${exportedModuleName}';`);
    });

    converter.importsWithPrefixes.forEach((prefix, importedModuleName) => {
      // Note: can't write the real word for import as it screws up system.js auto detection...
      preambleLines.push(
          `imp` +
          `ort * as ${prefix} from '${importedModuleName}';`);
    });

    const sm = emitSourceMaps ?
        ctx.toSourceMapGenerator(genFilePath, preambleLines.length).toJsComment() :
        '';
    const lines = [...preambleLines, ctx.toSource(), sm];
    if (sm) {
      // always add a newline at the end, as some tools have bugs without it.
      lines.push('');
    }
    ctx.setPreambleLineCount(preambleLines.length);
    return {sourceText: lines.join('\n'), context: ctx};
  }

  emitStatements(genFilePath: string, stmts: o.Statement[], preamble: string = '') {
    return this.emitStatementsAndContext(genFilePath, stmts, preamble).sourceText;
  }
}


class _TsEmitterVisitor extends AbstractEmitterVisitor implements o.TypeVisitor {
  private typeExpression = 0;

  constructor(private referenceFilter?: ReferenceFilter, private importFilter?: ReferenceFilter) {
    super(false);
  }

  importsWithPrefixes = new Map<string, string>();
  reexports = new Map<string, {name: string, as: string}[]>();

  visitType(t: o.Type|null, ctx: EmitterVisitorContext, defaultType: string = 'any') {
    if (t) {
      this.typeExpression++;
      t.visitType(this, ctx);
      this.typeExpression--;
    } else {
      ctx.print(null, defaultType);
    }
  }

  override visitLiteralExpr(ast: o.LiteralExpr, ctx: EmitterVisitorContext): any {
    const value = ast.value;
    if (value == null && ast.type != o.INFERRED_TYPE) {
      ctx.print(ast, `(${value} as any)`);
      return null;
    }
    return super.visitLiteralExpr(ast, ctx);
  }


  // Temporary workaround to support strictNullCheck enabled consumers of ngc emit.
  // In SNC mode, [] have the type never[], so we cast here to any[].
  // TODO: narrow the cast to a more explicit type, or use a pattern that does not
  // start with [].concat. see https://github.com/angular/angular/pull/11846
  override visitLiteralArrayExpr(ast: o.LiteralArrayExpr, ctx: EmitterVisitorContext): any {
    if (ast.entries.length === 0) {
      ctx.print(ast, '(');
    }
    const result = super.visitLiteralArrayExpr(ast, ctx);
    if (ast.entries.length === 0) {
      ctx.print(ast, ' as any[])');
    }
    return result;
  }

  override visitExternalExpr(ast: o.ExternalExpr, ctx: EmitterVisitorContext): any {
    this._visitIdentifier(ast.value, ast.typeParams, ctx);
    return null;
  }

  override visitAssertNotNullExpr(ast: o.AssertNotNull, ctx: EmitterVisitorContext): any {
    const result = super.visitAssertNotNullExpr(ast, ctx);
    ctx.print(ast, '!');
    return result;
  }

  override visitDeclareVarStmt(stmt: o.DeclareVarStmt, ctx: EmitterVisitorContext): any {
    if (stmt.hasModifier(o.StmtModifier.Exported) && stmt.value instanceof o.ExternalExpr &&
        !stmt.type) {
      // check for a reexport
      const {name, moduleName} = stmt.value.value;
      if (moduleName) {
        let reexports = this.reexports.get(moduleName);
        if (!reexports) {
          reexports = [];
          this.reexports.set(moduleName, reexports);
        }
        reexports.push({name: name!, as: stmt.name});
        return null;
      }
    }
    if (stmt.hasModifier(o.StmtModifier.Exported)) {
      ctx.print(stmt, `export `);
    }
    if (stmt.hasModifier(o.StmtModifier.Final)) {
      ctx.print(stmt, `const`);
    } else {
      ctx.print(stmt, `var`);
    }
    ctx.print(stmt, ` ${stmt.name}`);
    this._printColonType(stmt.type, ctx);
    if (stmt.value) {
      ctx.print(stmt, ` = `);
      stmt.value.visitExpression(this, ctx);
    }
    ctx.println(stmt, `;`);
    return null;
  }

  override visitWrappedNodeExpr(ast: o.WrappedNodeExpr<any>, ctx: EmitterVisitorContext): never {
    throw new Error('Cannot visit a WrappedNodeExpr when outputting Typescript.');
  }

  override visitCastExpr(ast: o.CastExpr, ctx: EmitterVisitorContext): any {
    ctx.print(ast, `(<`);
    ast.type!.visitType(this, ctx);
    ctx.print(ast, `>`);
    ast.value.visitExpression(this, ctx);
    ctx.print(ast, `)`);
    return null;
  }

  override visitInstantiateExpr(ast: o.InstantiateExpr, ctx: EmitterVisitorContext): any {
    ctx.print(ast, `new `);
    this.typeExpression++;
    ast.classExpr.visitExpression(this, ctx);
    this.typeExpression--;
    ctx.print(ast, `(`);
    this.visitAllExpressions(ast.args, ctx, ',');
    ctx.print(ast, `)`);
    return null;
  }

  override visitDeclareClassStmt(stmt: o.ClassStmt, ctx: EmitterVisitorContext): any {
    ctx.pushClass(stmt);
    if (stmt.hasModifier(o.StmtModifier.Exported)) {
      ctx.print(stmt, `export `);
    }
    ctx.print(stmt, `class ${stmt.name}`);
    if (stmt.parent != null) {
      ctx.print(stmt, ` extends `);
      this.typeExpression++;
      stmt.parent.visitExpression(this, ctx);
      this.typeExpression--;
    }
    ctx.println(stmt, ` {`);
    ctx.incIndent();
    stmt.fields.forEach((field) => this._visitClassField(field, ctx));
    if (stmt.constructorMethod != null) {
      this._visitClassConstructor(stmt, ctx);
    }
    stmt.getters.forEach((getter) => this._visitClassGetter(getter, ctx));
    stmt.methods.forEach((method) => this._visitClassMethod(method, ctx));
    ctx.decIndent();
    ctx.println(stmt, `}`);
    ctx.popClass();
    return null;
  }

  private _visitClassField(field: o.ClassField, ctx: EmitterVisitorContext) {
    if (field.hasModifier(o.StmtModifier.Private)) {
      // comment out as a workaround for #10967
      ctx.print(null, `/*private*/ `);
    }
    if (field.hasModifier(o.StmtModifier.Static)) {
      ctx.print(null, 'static ');
    }
    ctx.print(null, field.name);
    this._printColonType(field.type, ctx);
    if (field.initializer) {
      ctx.print(null, ' = ');
      field.initializer.visitExpression(this, ctx);
    }
    ctx.println(null, `;`);
  }

  private _visitClassGetter(getter: o.ClassGetter, ctx: EmitterVisitorContext) {
    if (getter.hasModifier(o.StmtModifier.Private)) {
      ctx.print(null, `private `);
    }
    ctx.print(null, `get ${getter.name}()`);
    this._printColonType(getter.type, ctx);
    ctx.println(null, ` {`);
    ctx.incIndent();
    this.visitAllStatements(getter.body, ctx);
    ctx.decIndent();
    ctx.println(null, `}`);
  }

  private _visitClassConstructor(stmt: o.ClassStmt, ctx: EmitterVisitorContext) {
    ctx.print(stmt, `constructor(`);
    this._visitParams(stmt.constructorMethod.params, ctx);
    ctx.println(stmt, `) {`);
    ctx.incIndent();
    this.visitAllStatements(stmt.constructorMethod.body, ctx);
    ctx.decIndent();
    ctx.println(stmt, `}`);
  }

  private _visitClassMethod(method: o.ClassMethod, ctx: EmitterVisitorContext) {
    if (method.hasModifier(o.StmtModifier.Private)) {
      ctx.print(null, `private `);
    }
    ctx.print(null, `${method.name}(`);
    this._visitParams(method.params, ctx);
    ctx.print(null, `)`);
    this._printColonType(method.type, ctx, 'void');
    ctx.println(null, ` {`);
    ctx.incIndent();
    this.visitAllStatements(method.body, ctx);
    ctx.decIndent();
    ctx.println(null, `}`);
  }

  override visitFunctionExpr(ast: o.FunctionExpr, ctx: EmitterVisitorContext): any {
    if (ast.name) {
      ctx.print(ast, 'function ');
      ctx.print(ast, ast.name);
    }
    ctx.print(ast, `(`);
    this._visitParams(ast.params, ctx);
    ctx.print(ast, `)`);
    this._printColonType(ast.type, ctx, 'void');
    if (!ast.name) {
      ctx.print(ast, ` => `);
    }
    ctx.println(ast, '{');
    ctx.incIndent();
    this.visitAllStatements(ast.statements, ctx);
    ctx.decIndent();
    ctx.print(ast, `}`);

    return null;
  }

  override visitDeclareFunctionStmt(stmt: o.DeclareFunctionStmt, ctx: EmitterVisitorContext): any {
    if (stmt.hasModifier(o.StmtModifier.Exported)) {
      ctx.print(stmt, `export `);
    }
    ctx.print(stmt, `function ${stmt.name}(`);
    this._visitParams(stmt.params, ctx);
    ctx.print(stmt, `)`);
    this._printColonType(stmt.type, ctx, 'void');
    ctx.println(stmt, ` {`);
    ctx.incIndent();
    this.visitAllStatements(stmt.statements, ctx);
    ctx.decIndent();
    ctx.println(stmt, `}`);
    return null;
  }

  override visitTryCatchStmt(stmt: o.TryCatchStmt, ctx: EmitterVisitorContext): any {
    ctx.println(stmt, `try {`);
    ctx.incIndent();
    this.visitAllStatements(stmt.bodyStmts, ctx);
    ctx.decIndent();
    ctx.println(stmt, `} catch (${CATCH_ERROR_VAR.name}) {`);
    ctx.incIndent();
    const catchStmts =
        [<o.Statement>CATCH_STACK_VAR.set(CATCH_ERROR_VAR.prop('stack', null)).toDeclStmt(null, [
          o.StmtModifier.Final
        ])].concat(stmt.catchStmts);
    this.visitAllStatements(catchStmts, ctx);
    ctx.decIndent();
    ctx.println(stmt, `}`);
    return null;
  }

  visitBuiltinType(type: o.BuiltinType, ctx: EmitterVisitorContext): any {
    let typeStr: string;
    switch (type.name) {
      case o.BuiltinTypeName.Bool:
        typeStr = 'boolean';
        break;
      case o.BuiltinTypeName.Dynamic:
        typeStr = 'any';
        break;
      case o.BuiltinTypeName.Function:
        typeStr = 'Function';
        break;
      case o.BuiltinTypeName.Number:
        typeStr = 'number';
        break;
      case o.BuiltinTypeName.Int:
        typeStr = 'number';
        break;
      case o.BuiltinTypeName.String:
        typeStr = 'string';
        break;
      case o.BuiltinTypeName.None:
        typeStr = 'never';
        break;
      default:
        throw new Error(`Unsupported builtin type ${type.name}`);
    }
    ctx.print(null, typeStr);
    return null;
  }

  visitExpressionType(ast: o.ExpressionType, ctx: EmitterVisitorContext): any {
    ast.value.visitExpression(this, ctx);
    if (ast.typeParams !== null) {
      ctx.print(null, '<');
      this.visitAllObjects(type => this.visitType(type, ctx), ast.typeParams, ctx, ',');
      ctx.print(null, '>');
    }
    return null;
  }

  visitArrayType(type: o.ArrayType, ctx: EmitterVisitorContext): any {
    this.visitType(type.of, ctx);
    ctx.print(null, `[]`);
    return null;
  }

  visitMapType(type: o.MapType, ctx: EmitterVisitorContext): any {
    ctx.print(null, `{[key: string]:`);
    this.visitType(type.valueType, ctx);
    ctx.print(null, `}`);
    return null;
  }

  override getBuiltinMethodName(method: o.BuiltinMethod): string {
    let name: string;
    switch (method) {
      case o.BuiltinMethod.ConcatArray:
        name = 'concat';
        break;
      case o.BuiltinMethod.SubscribeObservable:
        name = 'subscribe';
        break;
      case o.BuiltinMethod.Bind:
        name = 'bind';
        break;
      default:
        throw new Error(`Unknown builtin method: ${method}`);
    }
    return name;
  }

  private _visitParams(params: o.FnParam[], ctx: EmitterVisitorContext): void {
    this.visitAllObjects(param => {
      ctx.print(null, param.name);
      this._printColonType(param.type, ctx);
    }, params, ctx, ',');
  }

  private _visitIdentifier(
      value: o.ExternalReference, typeParams: o.Type[]|null, ctx: EmitterVisitorContext): void {
    const {name, moduleName} = value;
    if (this.referenceFilter && this.referenceFilter(value)) {
      ctx.print(null, '(null as any)');
      return;
    }
    if (moduleName && (!this.importFilter || !this.importFilter(value))) {
      let prefix = this.importsWithPrefixes.get(moduleName);
      if (prefix == null) {
        prefix = `i${this.importsWithPrefixes.size}`;
        this.importsWithPrefixes.set(moduleName, prefix);
      }
      ctx.print(null, `${prefix}.`);
    }
    ctx.print(null, name!);

    if (this.typeExpression > 0) {
      // If we are in a type expression that refers to a generic type then supply
      // the required type parameters. If there were not enough type parameters
      // supplied, supply any as the type. Outside a type expression the reference
      // should not supply type parameters and be treated as a simple value reference
      // to the constructor function itself.
      const suppliedParameters = typeParams || [];
      if (suppliedParameters.length > 0) {
        ctx.print(null, `<`);
        this.visitAllObjects(type => type.visitType(this, ctx), typeParams!, ctx, ',');
        ctx.print(null, `>`);
      }
    }
  }

  private _printColonType(type: o.Type|null, ctx: EmitterVisitorContext, defaultType?: string) {
    if (type !== o.INFERRED_TYPE) {
      ctx.print(null, ':');
      this.visitType(type, ctx, defaultType);
    }
  }
}