/*
Copyright 2022 The Apex Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

import {
  Context,
  BaseVisitor,
  Kind,
  Type,
  Optional,
  Writer,
  AnyType,
  Alias,
  List,
  Map,
} from "@apexlang/core/model";
import { defaultValueForType, expandType, mapArg, mapArgs } from "./helpers.js";
import {
  isHandler,
  isProvider,
  noCode,
  isVoid,
  snakeCase,
} from "../utils/index.js";

export class ScaffoldVisitor extends BaseVisitor {
  visitNamespaceBefore(context: Context): void {
    this.write(`#!/usr/bin/env python3\n`);
    const adapter = new AdapterTypesVisitor(this.writer);
    context.namespace.accept(context, adapter);
    const types = new TypesVisitor(this.writer);
    context.namespace.accept(context, types);
    this.write(`\n`);
  }

  visitNamespaceAfter(context: Context): void {
    const main = new MainVisitor(this.writer);
    context.namespace.accept(context, main);

    this.write(`\n\nif __name__ == "__main__":
\tmain()
\n`);
  }

  visitInterfaceBefore(context: Context): void {
    if (!isHandler(context)) {
      return;
    }
    const impl = new ImplVisitor(this.writer);
    context.interface.accept(context, impl);
  }
}

class MainVisitor extends BaseVisitor {
  visitNamespaceBefore(context: Context): void {
    this.write(`def main():\n`);
  }

  visitInterfaceBefore(context: Context): void {
    if (!isHandler(context)) {
      return;
    }
    super.triggerInterfaceBefore(context);
    const name = context.interface.name;
    this.write(`\tregister_${snakeCase(name)}(${name}Impl())\n`);
  }

  visitNamespaceAfter(context: Context): void {
    this.write(`\n\tstart()\n`);
  }
}

class ImplVisitor extends BaseVisitor {
  private stateful: boolean;

  constructor(writer: Writer, stateful: boolean = false) {
    super(writer);
    this.stateful = stateful;
  }

  visitInterfaceBefore(context: Context): void {
    if (!isHandler(context)) {
      return;
    }
    super.triggerInterfaceBefore(context);
    const name = context.interface.name;
    this.write(`class ${name}Impl(${name}):\n`);
  }

  visitOperation(context: Context): void {
    this.write(`\n`);
    const { interface: iface, operation } = context;
    if (noCode(operation)) {
      return;
    }
    let opVal = "";
    opVal += `\tasync def ${snakeCase(operation.name)}(self`;
    if (this.stateful) {
      opVal += ", ctx: Context";
    }
    if (operation.parameters.length > 0) {
      opVal += ", ";
    }
    if (operation.isUnary()) {
      opVal += mapArg(operation.unaryOp());
    } else {
      opVal += mapArgs(operation.parameters);
    }
    opVal += `)`;
    if (!isVoid(operation.type)) {
      opVal += ` -> ${expandType(operation.type, true)}`;
    }
    opVal += `:\n`;
    this.write(opVal);
    if (!isVoid(operation.type)) {
      const dv = defaultValueForType(operation.type);
      this.write(`\t\treturn ${dv};`);
    } else {
      this.write(`\t\treturn\n`);
    }
    this.write(`\n`);
    super.triggerOperation(context);
  }

  visitInterfaceAfter(context: Context): void {
    this.write(`\n\n`);
  }
}

class AdapterTypesVisitor extends BaseVisitor {
  visitNamespaceBefore(content: Context): void {
    this.write(`from adapter import start`);
  }
  visitInterface(context: Context): void {
    const { interface: iface } = context;
    if (isHandler(context)) {
      this.write(`, register_${snakeCase(iface.name)}`);
    }
    if (isProvider(context)) {
      this.write(`, ${snakeCase(iface.name)}`);
    }
  }
  visitNamespaceAfter(content: Context): void {
    this.write(`\n`);
  }
}

class TypesVisitor extends BaseVisitor {
  hasObjects: boolean = false;
  found: Set<string> = new Set<string>();

  visitNamespaceBefore(context: Context): void {}

  private addImport(name: string): void {
    if (!this.found.has(name)) {
      this.found.add(name);
      if (!this.hasObjects) {
        this.write(`from interfaces import `);
        this.hasObjects = true;
      } else {
        this.write(`, `);
      }
      this.write(name);
    }
  }

  addType(t: AnyType): void {
    if (t.kind == Kind.Alias) {
      t = (t as Alias).type;
    }
    switch (t.kind) {
      case Kind.Type:
        const v = t as Type;
        this.addImport(v.name);
        break;
      case Kind.Optional:
        const o = t as Optional;
        this.addType(o.type);
        break;
      case Kind.List:
        const l = t as List;
        this.addType(l.type);
        break;
      case Kind.Map:
        const m = t as Map;
        this.addType(m.keyType);
        this.addType(m.valueType);
    }
  }

  visitInterface(context: Context): void {
    const { interface: iface } = context;
    if (isHandler(context)) {
      this.addImport(iface.name);
    }
  }

  visitOperation(context: Context): void {
    const operation = context.operation!;
    this.addType(operation.type);
  }

  visitParameter(context: Context): void {
    const parameter = context.parameter!;
    this.addType(parameter.type);
  }

  visitNamespaceAfter(context: Context): void {
    if (this.hasObjects) {
      this.write(`\n\n`);
    }
  }
}