use std::ops::Deref;
use std::path::PathBuf;

use clap::{CommandFactory, Parser, Subcommand};

pub struct Args {
    inner: ArgsInner,
}

#[derive(Parser)]
pub struct ArgsInner {
    #[clap(subcommand)]
    pub command: Command,
}

#[derive(Subcommand)]
pub enum Command {
    Lex {
        input: PathBuf,
        output_tokens: PathBuf,
        output_symbols: PathBuf,
    },
    Syn {
        input: PathBuf,
        output_tree: PathBuf,
    },
    Sem {
        input: PathBuf,
        output_tree: PathBuf,
    },
    Gen {
        mode: GenMode,
        #[clap(short, long, default_value_t = false)]
        optimize: bool,
        input: PathBuf,
        output: PathBuf,
        output_symbols: PathBuf,
    },
    Com {
        #[clap(short, long, default_value_t = false)]
        optimize: bool,
        input: PathBuf,
        output: PathBuf,
    },
    Int {
        input: PathBuf,
    },
}

#[derive(Copy, Clone, PartialEq, Eq, clap::ValueEnum)]
pub enum GenMode {
    #[clap(name = "intermediate", alias = "i")]
    Intermediate,
    #[clap(name = "postfix", alias = "p")]
    Postfix,
}

impl Args {
    pub fn parse() -> Self {
        let inner = match validate_inner(ArgsInner::parse()) {
            Ok(args) => args,
            Err(err) => {
                let mut command = ArgsInner::command();
                err.format(&mut command).exit();
            },
        };

        Self { inner }
    }
}

impl Deref for Args {
    type Target = ArgsInner;

    fn deref(&self) -> &Self::Target {
        &self.inner
    }
}

fn validate_inner(args: ArgsInner) -> Result<ArgsInner, clap::Error> {
    match &args.command {
        Command::Lex {
            input,
            output_tokens,
            output_symbols,
        } => validate_lex(input, output_tokens, output_symbols)?,
        Command::Syn { input, output_tree } => validate_syn(input, output_tree)?,
        Command::Sem { input, output_tree } => validate_sem(input, output_tree)?,
        Command::Gen {
            input,
            output,
            output_symbols,
            ..
        } => validate_gen(input, output, output_symbols)?,
        Command::Com { input, output, .. } => validate_com(input, output)?,
        Command::Int { input } => validate_int(input)?,
    };

    Ok(args)
}

fn validate_lex(
    input: &PathBuf,
    output_tokens: &PathBuf,
    output_symbols: &PathBuf,
) -> Result<(), clap::Error> {
    if !input.is_file() {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            format!("Input file '{}' does not exist", input.display()),
        ));
    }

    if input == output_tokens {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            "Input and output files cannot be the same",
        ));
    }

    if input == output_symbols {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            "Input and output files cannot be the same",
        ));
    };

    Ok(())
}

fn validate_syn(input: &PathBuf, output_tree: &PathBuf) -> Result<(), clap::Error> {
    if !input.is_file() {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            format!("Input file '{}' does not exist", input.display()),
        ));
    }

    if output_tree == input {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            "Input and output files cannot be the same",
        ));
    };

    Ok(())
}

fn validate_sem(input: &PathBuf, output_tree: &PathBuf) -> Result<(), clap::Error> {
    if !input.is_file() {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            format!("Input file '{}' does not exist", input.display()),
        ));
    }

    if output_tree == input {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            "Input and output files cannot be the same",
        ));
    };

    Ok(())
}

fn validate_gen(
    input: &PathBuf,
    output: &PathBuf,
    output_symbols: &PathBuf,
) -> Result<(), clap::Error> {
    if !input.is_file() {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            format!("Input file '{}' does not exist", input.display()),
        ));
    }

    if input == output {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            "Input and output files cannot be the same",
        ));
    };

    if input == output_symbols {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            "Input and output files cannot be the same",
        ));
    };

    Ok(())
}

fn validate_com(input: &PathBuf, output: &PathBuf) -> Result<(), clap::Error> {
    if !input.is_file() {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            format!("Input file '{}' does not exist", input.display()),
        ));
    }

    if input == output {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            "Input and output files cannot be the same",
        ));
    };

    Ok(())
}

fn validate_int(input: &PathBuf) -> Result<(), clap::Error> {
    if !input.is_file() {
        return Err(clap::Error::raw(
            clap::error::ErrorKind::InvalidValue,
            format!("Input file '{}' does not exist", input.display()),
        ));
    }

    Ok(())
}