use anyhow::{Context, Result};
use frontmatter_gen::Frontmatter;
use std::{env, fs, process::Command};

use clap::{Parser, Subcommand};

/// A CLI for managing notes
#[derive(Parser)]
#[command(name = "notes")]
struct Cli {
  #[command(subcommand)]
  command: Commands,
}

#[derive(Subcommand)]
enum Commands {
  /// Creates a new note based on the latest note in the directory
  New(NewArg),
}

#[derive(Parser)]
struct NewArg {
  /// Creates the note file without opening it for editing.
  ///
  /// By default the new note file is immediately opened for editing with the default EDITOR. This flag prevents the
  /// note from being opened, and only creates it.
  #[clap(long, action)]
  no_open: bool,
}

fn main() -> Result<()> {
  let args = Cli::parse();

  match args.command {
    Commands::New(arg) => {
      let mut frontmatter = fs::read_dir(".")?
        .filter_map(|e| e.ok())
        .filter(|e| {
          e.file_type().is_ok_and(|t| t.is_file()) && e.file_name().to_str().is_some_and(|f| f.ends_with(".md"))
        })
        .max_by_key(|e| e.file_name())
        .and_then(|e| {
          frontmatter_gen::extract(&fs::read_to_string(e.path()).ok()?)
            .ok()
            .map(|(f, _)| f)
        })
        .unwrap_or_else(Frontmatter::new);

      let now = chrono::Local::now();
      frontmatter.insert(
        "date".to_owned(),
        frontmatter_gen::Value::String(now.format("%F").to_string()),
      );

      let path = format!("{}.md", now.format("%FT%H%M%S"));
      let contents = format!(
        "\
          ---\n\
          {}\n\
          ---\n\
          \n\
          \n\
          ",
        frontmatter_gen::to_format(&frontmatter, frontmatter_gen::Format::Yaml)?
      );
      fs::write(&path, &contents)?;

      if !arg.no_open {
        let editor = env::var("EDITOR").context("No EDITOR variable defined.")?;
        let editor_args = shlex::split(&editor).context("Invalid EDITOR variable.")?;
        _ = Command::new(&editor_args[0])
          .args(&editor_args[1..])
          .arg(format!("{path}:{}", contents.matches('\n').count()))
          .status()?;
      }
    }
  }

  Ok(())
}