/*
 This file is part of GNU Taler
 (C) 2019 GNUnet e.V.

 GNU Taler is free software; you can redistribute it and/or modify it under the
 terms of the GNU General Public License as published by the Free Software
 Foundation; either version 3, or (at your option) any later version.

 GNU Taler is distributed in the hope that it will be useful, but WITHOUT ANY
 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
 A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

 You should have received a copy of the GNU General Public License along with
 GNU Taler; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
 */

/**
 * Imports.
 */
import process from "process";
import path from "path";
import readline from "readline";

class Converter<T> {}

export const INT = new Converter<number>();
export const STRING: Converter<string> = new Converter<string>();

export interface OptionArgs<T> {
  help?: string;
  default?: T;
  onPresentHandler?: (v: T) => void;
}

export interface ArgumentArgs<T> {
  metavar?: string;
  help?: string;
  default?: T;
}

export interface SubcommandArgs {
  help?: string;
}

export interface FlagArgs {
  help?: string;
}

export interface ProgramArgs {
  help?: string;
}

interface ArgumentDef {
  name: string;
  conv: Converter<any>;
  args: ArgumentArgs<any>;
  required: boolean;
}

interface SubcommandDef {
  commandGroup: CommandGroup<any, any>;
  name: string;
  args: SubcommandArgs;
}

type ActionFn<TG> = (x: TG) => void;

type SubRecord<S extends keyof any, N extends keyof any, V> = {
  [Y in S]: { [X in N]: V };
};

interface OptionDef {
  name: string;
  flagspec: string[];
  /**
   * Converter, only present for options, not for flags.
   */
  conv?: Converter<any>;
  args: OptionArgs<any>;
  isFlag: boolean;
  required: boolean;
}

function splitOpt(opt: string): { key: string; value?: string } {
  const idx = opt.indexOf("=");
  if (idx == -1) {
    return { key: opt };
  }
  return { key: opt.substring(0, idx), value: opt.substring(idx + 1) };
}

function formatListing(key: string, value?: string): string {
  const res = "  " + key;
  if (!value) {
    return res;
  }
  if (res.length >= 25) {
    return res + "\n" + "    " + value;
  } else {
    return res.padEnd(24) + " " + value;
  }
}

export class CommandGroup<GN extends keyof any, TG> {
  private shortOptions: { [name: string]: OptionDef } = {};
  private longOptions: { [name: string]: OptionDef } = {};
  private subcommandMap: { [name: string]: SubcommandDef } = {};
  private subcommands: SubcommandDef[] = [];
  private options: OptionDef[] = [];
  private arguments: ArgumentDef[] = [];

  private myAction?: ActionFn<TG>;

  constructor(
    private argKey: string,
    private name: string | null,
    private scArgs: SubcommandArgs,
  ) {}

  action(f: ActionFn<TG>): void {
    if (this.myAction) {
      throw Error("only one action supported per command");
    }
    this.myAction = f;
  }

  requiredOption<N extends keyof any, V>(
    name: N,
    flagspec: string[],
    conv: Converter<V>,
    args: OptionArgs<V> = {},
  ): CommandGroup<GN, TG & SubRecord<GN, N, V>> {
    const def: OptionDef = {
      args: args,
      conv: conv,
      flagspec: flagspec,
      isFlag: false,
      required: true,
      name: name as string,
    };
    this.options.push(def);
    for (const flag of flagspec) {
      if (flag.startsWith("--")) {
        const flagname = flag.substring(2);
        this.longOptions[flagname] = def;
      } else if (flag.startsWith("-")) {
        const flagname = flag.substring(1);
        this.shortOptions[flagname] = def;
      } else {
        throw Error("option must start with '-' or '--'");
      }
    }
    return this as any;
  }

  maybeOption<N extends keyof any, V>(
    name: N,
    flagspec: string[],
    conv: Converter<V>,
    args: OptionArgs<V> = {},
  ): CommandGroup<GN, TG & SubRecord<GN, N, V | undefined>> {
    const def: OptionDef = {
      args: args,
      conv: conv,
      flagspec: flagspec,
      isFlag: false,
      required: false,
      name: name as string,
    };
    this.options.push(def);
    for (const flag of flagspec) {
      if (flag.startsWith("--")) {
        const flagname = flag.substring(2);
        this.longOptions[flagname] = def;
      } else if (flag.startsWith("-")) {
        const flagname = flag.substring(1);
        this.shortOptions[flagname] = def;
      } else {
        throw Error("option must start with '-' or '--'");
      }
    }
    return this as any;
  }

  requiredArgument<N extends keyof any, V>(
    name: N,
    conv: Converter<V>,
    args: ArgumentArgs<V> = {},
  ): CommandGroup<GN, TG & SubRecord<GN, N, V>> {
    const argDef: ArgumentDef = {
      args: args,
      conv: conv,
      name: name as string,
      required: true,
    };
    this.arguments.push(argDef);
    return this as any;
  }

  maybeArgument<N extends keyof any, V>(
    name: N,
    conv: Converter<V>,
    args: ArgumentArgs<V> = {},
  ): CommandGroup<GN, TG & SubRecord<GN, N, V | undefined>> {
    const argDef: ArgumentDef = {
      args: args,
      conv: conv,
      name: name as string,
      required: false,
    };
    this.arguments.push(argDef);
    return this as any;
  }

  flag<N extends string, V>(
    name: N,
    flagspec: string[],
    args: OptionArgs<V> = {},
  ): CommandGroup<GN, TG & SubRecord<GN, N, boolean>> {
    const def: OptionDef = {
      args: args,
      flagspec: flagspec,
      isFlag: true,
      required: false,
      name: name as string,
    };
    this.options.push(def);
    for (const flag of flagspec) {
      if (flag.startsWith("--")) {
        const flagname = flag.substring(2);
        this.longOptions[flagname] = def;
      } else if (flag.startsWith("-")) {
        const flagname = flag.substring(1);
        this.shortOptions[flagname] = def;
      } else {
        throw Error("option must start with '-' or '--'");
      }
    }
    return this as any;
  }

  subcommand<GN extends keyof any>(
    argKey: GN,
    name: string,
    args: SubcommandArgs = {},
  ): CommandGroup<GN, TG> {
    const cg = new CommandGroup<GN, {}>(argKey as string, name, args);
    const def: SubcommandDef = {
      commandGroup: cg,
      name: name as string,
      args: args,
    };
    cg.flag("help", ["-h", "--help"], {
      help: "Show this message and exit.",
    });
    this.subcommandMap[name as string] = def;
    this.subcommands.push(def);
    this.subcommands = this.subcommands.sort((x1, x2) => {
      const a = x1.name;
      const b = x2.name;
      if (a === b) {
        return 0;
      } else if (a < b) {
        return -1;
      } else {
        return 1;
      }
    });
    return cg as any;
  }

  printHelp(progName: string, parents: CommandGroup<any, any>[]): void {
    let usageSpec = "";
    for (const p of parents) {
      usageSpec += (p.name ?? progName) + " ";
      if (p.arguments.length >= 1) {
        usageSpec += "<ARGS...> ";
      }
    }
    usageSpec += (this.name ?? progName) + " ";
    if (this.subcommands.length != 0) {
      usageSpec += "COMMAND ";
    }
    for (const a of this.arguments) {
      const argName = a.args.metavar ?? a.name;
      usageSpec += `<${argName}> `;
    }
    usageSpec = usageSpec.trimRight();
    console.log(`Usage: ${usageSpec}`);
    if (this.scArgs.help) {
      console.log();
      console.log(this.scArgs.help);
    }
    if (this.options.length != 0) {
      console.log();
      console.log("Options:");
      for (const opt of this.options) {
        let optSpec = opt.flagspec.join(", ");
        if (!opt.isFlag) {
          optSpec = optSpec + "=VALUE";
        }
        console.log(formatListing(optSpec, opt.args.help));
      }
    }

    if (this.subcommands.length != 0) {
      console.log();
      console.log("Commands:");
      for (const subcmd of this.subcommands) {
        console.log(formatListing(subcmd.name, subcmd.args.help));
      }
    }
  }

  /**
   * Run the (sub-)command with the given command line parameters.
   */
  run(
    progname: string,
    parents: CommandGroup<any, any>[],
    unparsedArgs: string[],
    parsedArgs: any,
  ): void {
    let posArgIndex = 0;
    let argsTerminated = false;
    let i;
    let foundSubcommand: CommandGroup<any, any> | undefined = undefined;
    const myArgs: any = (parsedArgs[this.argKey] = {});
    const foundOptions: { [name: string]: boolean } = {};
    const currentName = this.name ?? progname;
    for (i = 0; i < unparsedArgs.length; i++) {
      const argVal = unparsedArgs[i];
      if (argsTerminated == false) {
        if (argVal === "--") {
          argsTerminated = true;
          continue;
        }
        if (argVal.startsWith("--")) {
          const opt = argVal.substring(2);
          const r = splitOpt(opt);
          const d = this.longOptions[r.key];
          if (!d) {
            console.error(
              `error: unknown option '--${r.key}' for ${currentName}`,
            );
            process.exit(-1);
            throw Error("not reached");
          }
          if (d.isFlag) {
            if (r.value !== undefined) {
              console.error(`error: flag '--${r.key}' does not take a value`);
              process.exit(-1);
              throw Error("not reached");
            }
            foundOptions[d.name] = true;
            myArgs[d.name] = true;
          } else {
            if (r.value === undefined) {
              if (i === unparsedArgs.length - 1) {
                console.error(`error: option '--${r.key}' needs an argument`);
                process.exit(-1);
                throw Error("not reached");
              }
              myArgs[d.name] = unparsedArgs[i + 1];
              i++;
            } else {
              myArgs[d.name] = r.value;
            }
            foundOptions[d.name] = true;
          }
          continue;
        }
        if (argVal.startsWith("-") && argVal != "-") {
          const optShort = argVal.substring(1);
          for (let si = 0; si < optShort.length; si++) {
            const chr = optShort[si];
            const opt = this.shortOptions[chr];
            if (!opt) {
              console.error(`error: option '-${chr}' not known`);
              process.exit(-1);
            }
            if (opt.isFlag) {
              myArgs[opt.name] = true;
              foundOptions[opt.name] = true;
            } else {
              if (si == optShort.length - 1) {
                if (i === unparsedArgs.length - 1) {
                  console.error(`error: option '-${chr}' needs an argument`);
                  process.exit(-1);
                  throw Error("not reached");
                } else {
                  myArgs[opt.name] = unparsedArgs[i + 1];
                  i++;
                }
              } else {
                myArgs[opt.name] = optShort.substring(si + 1);
              }
              foundOptions[opt.name] = true;
              break;
            }
          }
          continue;
        }
      }
      if (this.subcommands.length != 0) {
        const subcmd = this.subcommandMap[argVal];
        if (!subcmd) {
          console.error(`error: unknown command '${argVal}'`);
          process.exit(-1);
          throw Error("not reached");
        }
        foundSubcommand = subcmd.commandGroup;
        break;
      } else {
        const d = this.arguments[posArgIndex];
        if (!d) {
          console.error(`error: too many arguments for ${currentName}`);
          process.exit(-1);
          throw Error("not reached");
        }
        myArgs[d.name] = unparsedArgs[i];
        posArgIndex++;
      }
    }

    if (parsedArgs[this.argKey].help) {
      this.printHelp(progname, parents);
      process.exit(0);
      throw Error("not reached");
    }

    for (let i = posArgIndex; i < this.arguments.length; i++) {
      const d = this.arguments[i];
      if (d.required) {
        if (d.args.default !== undefined) {
          myArgs[d.name] = d.args.default;
        } else {
          console.error(
            `error: missing positional argument '${d.name}' for ${currentName}`,
          );
          process.exit(-1);
          throw Error("not reached");
        }
      }
    }

    for (const option of this.options) {
      if (option.isFlag == false && option.required == true) {
        if (!foundOptions[option.name]) {
          if (option.args.default !== undefined) {
            myArgs[option.name] = option.args.default;
          } else {
            const name = option.flagspec.join(",");
            console.error(`error: missing option '${name}'`);
            process.exit(-1);
            throw Error("not reached");
          }
        }
      }
    }

    for (const option of this.options) {
      const ph = option.args.onPresentHandler;
      if (ph && foundOptions[option.name]) {
        ph(myArgs[option.name]);
      }
    }

    if (foundSubcommand) {
      foundSubcommand.run(
        progname,
        Array.prototype.concat(parents, [this]),
        unparsedArgs.slice(i + 1),
        parsedArgs,
      );
    } else if (this.myAction) {
      let r;
      try {
        r = this.myAction(parsedArgs);
      } catch (e) {
        console.error(`An error occurred while running ${currentName}`);
        console.error(e);
        process.exit(1);
      }
      Promise.resolve(r).catch((e) => {
        console.error(`An error occurred while running ${currentName}`);
        console.error(e);
        process.exit(1);
      });
    } else {
      this.printHelp(progname, parents);
      process.exit(-1);
      throw Error("not reached");
    }
  }
}

export class Program<PN extends keyof any, T> {
  private mainCommand: CommandGroup<any, any>;

  constructor(argKey: string, args: ProgramArgs = {}) {
    this.mainCommand = new CommandGroup<any, any>(argKey, null, {
      help: args.help,
    });
    this.mainCommand.flag("help", ["-h", "--help"], {
      help: "Show this message and exit.",
    });
  }

  run(): void {
    const args = process.argv;
    if (args.length < 2) {
      console.error(
        "Error while parsing command line arguments: not enough arguments",
      );
      process.exit(-1);
    }
    const progname = path.basename(args[1]);
    const rest = args.slice(2);

    this.mainCommand.run(progname, [], rest, {});
  }

  subcommand<GN extends keyof any>(
    argKey: GN,
    name: string,
    args: SubcommandArgs = {},
  ): CommandGroup<GN, T> {
    const cmd = this.mainCommand.subcommand(argKey, name as string, args);
    return cmd as any;
  }

  requiredOption<N extends keyof any, V>(
    name: N,
    flagspec: string[],
    conv: Converter<V>,
    args: OptionArgs<V> = {},
  ): Program<PN, T & SubRecord<PN, N, V>> {
    this.mainCommand.requiredOption(name, flagspec, conv, args);
    return this as any;
  }

  maybeOption<N extends keyof any, V>(
    name: N,
    flagspec: string[],
    conv: Converter<V>,
    args: OptionArgs<V> = {},
  ): Program<PN, T & SubRecord<PN, N, V | undefined>> {
    this.mainCommand.maybeOption(name, flagspec, conv, args);
    return this as any;
  }

  /**
   * Add a flag (option without value) to the program.
   */
  flag<N extends string>(
    name: N,
    flagspec: string[],
    args: OptionArgs<boolean> = {},
  ): Program<PN, T & SubRecord<PN, N, boolean>> {
    this.mainCommand.flag(name, flagspec, args);
    return this as any;
  }

  /**
   * Add a required positional argument to the program.
   */
  requiredArgument<N extends keyof any, V>(
    name: N,
    conv: Converter<V>,
    args: ArgumentArgs<V> = {},
  ): Program<N, T & SubRecord<PN, N, V>> {
    this.mainCommand.requiredArgument(name, conv, args);
    return this as any;
  }

  /**
   * Add an optional argument to the program.
   */
  maybeArgument<N extends keyof any, V>(
    name: N,
    conv: Converter<V>,
    args: ArgumentArgs<V> = {},
  ): Program<N, T & SubRecord<PN, N, V | undefined>> {
    this.mainCommand.maybeArgument(name, conv, args);
    return this as any;
  }
}

export type GetArgType<T> = T extends Program<any, infer AT>
  ? AT
  : T extends CommandGroup<any, infer AT>
  ? AT
  : any;

export function program<PN extends keyof any>(
  argKey: PN,
  args: ProgramArgs = {},
): Program<PN, {}> {
  return new Program(argKey as string, args);
}

export function prompt(question: string): Promise<string> {
  const stdinReadline = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
  });
  return new Promise<string>((resolve, reject) => {
    stdinReadline.question(question, (res) => {
      resolve(res);
      stdinReadline.close();
    });
  });
}