/*
 * Copyright 2024, gRPC Authors All rights reserved.
 *
 * 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 Foundation
import SwiftProtobuf
import SwiftProtobufPluginLibrary

import struct GRPCCodeGen.CodeGenerationRequest

/// Parses a ``FileDescriptor`` object into a ``CodeGenerationRequest`` object.
internal struct ProtobufCodeGenParser {
  internal init() {}
  internal func parse(input: FileDescriptor) throws -> CodeGenerationRequest {
    var header = input.header
    // Ensuring there is a blank line after the header.
    if !header.isEmpty && !header.hasSuffix("\n\n") {
      header.append("\n")
    }
    let leadingTrivia = """
      // DO NOT EDIT.
      // swift-format-ignore-file
      //
      // Generated by the gRPC Swift generator plugin for the protocol buffer compiler.
      // Source: \(input.name)
      //
      // For information on using the generated types, please see the documentation:
      //   https://github.com/grpc/grpc-swift

      """
    var dependencies = input.dependencies.map {
      CodeGenerationRequest.Dependency(module: $0.name)
    }
    dependencies.append(CodeGenerationRequest.Dependency(module: "GRPCProtobuf"))
    let lookupSerializer: (String) -> String = { messageType in
      "ProtobufSerializer<\(messageType)>()"
    }
    let lookupDeserializer: (String) -> String = { messageType in
      "ProtobufDeserializer<\(messageType)>()"
    }
    let services = input.services.map {
      CodeGenerationRequest.ServiceDescriptor(descriptor: $0, package: input.package)
    }

    return CodeGenerationRequest(
      fileName: input.name,
      leadingTrivia: header + leadingTrivia,
      dependencies: dependencies,
      services: services,
      lookupSerializer: lookupSerializer,
      lookupDeserializer: lookupDeserializer
    )
  }
}

extension CodeGenerationRequest.ServiceDescriptor {
  fileprivate init(descriptor: ServiceDescriptor, package: String) {
    let methods = descriptor.methods.map {
      CodeGenerationRequest.ServiceDescriptor.MethodDescriptor(descriptor: $0)
    }
    let name = CodeGenerationRequest.Name(
      base: descriptor.name,
      generatedUpperCase: NamingUtils.toUpperCamelCase(descriptor.name),
      generatedLowerCase: NamingUtils.toLowerCamelCase(descriptor.name)
    )
    let namespace = CodeGenerationRequest.Name(
      base: package,
      generatedUpperCase: NamingUtils.toUpperCamelCase(package),
      generatedLowerCase: NamingUtils.toLowerCamelCase(package)
    )
    let documentation = descriptor.protoSourceComments()
    self.init(documentation: documentation, name: name, namespace: namespace, methods: methods)
  }
}

extension CodeGenerationRequest.ServiceDescriptor.MethodDescriptor {
  fileprivate init(descriptor: MethodDescriptor) {
    let name = CodeGenerationRequest.Name(
      base: descriptor.name,
      generatedUpperCase: NamingUtils.toUpperCamelCase(descriptor.name),
      generatedLowerCase: NamingUtils.toLowerCamelCase(descriptor.name)
    )
    let documentation = descriptor.protoSourceComments()
    self.init(
      documentation: documentation,
      name: name,
      isInputStreaming: descriptor.clientStreaming,
      isOutputStreaming: descriptor.serverStreaming,
      inputType: descriptor.inputType.name,
      outputType: descriptor.outputType.name
    )
  }
}

extension FileDescriptor {
  fileprivate var header: String {
    var header = String()
    // Field number used to collect the syntax field which is usually the first
    // declaration in a.proto file.
    // See more here:
    // https://github.com/apple/swift-protobuf/blob/main/Protos/SwiftProtobuf/google/protobuf/descriptor.proto
    let syntaxPath = IndexPath(index: 12)
    if let syntaxLocation = self.sourceCodeInfoLocation(path: syntaxPath) {
      header = syntaxLocation.asSourceComment(
        commentPrefix: "///",
        leadingDetachedPrefix: "//"
      )
    }
    return header
  }
}