/*!
output first or last n lines, like a head and tail of linux command.

# Features

- output first or last n lines, like a head and tail of linux command.
- minimum support rustc 1.56.1 (59eed8a2a 2021-11-01)

# Command help

```text
aki-unbody --help
```

```text
Usage:
  aki-unbody [options]

output first or last n lines, like a head and tail of linux command.

Options:
  -h, --head <num>      output the first <num> lines.
  -t, --tail <num>      output the last <num> lines.
  -i, --inverse         output the body, except for head and tail.

  -H, --help        display this help and exit
  -V, --version     display version information and exit

Examples:
  Outputs first 2 lines:
    cat file1.txt | aki-unbody --head 2
  Outputs last 2 lines:
    cat file1.txt | aki-unbody --tail 2
  Outputs body, except for first 2 lines and last 2 lines:
    cat file1.txt | aki-unbody --head 2 --tail 2 --inverse
```

# Quick install

1. you can install this into cargo bin path:

```text
cargo install aki-unbody
```

2. you can build debian package:

```text
cargo deb
```

and install **.deb** into your local repository of debian package.

# Examples

The input data used in this example looks like this:

```text
cat file1.txt
```

result output:
```text
LN:0001,text
LN:0002,text
LN:0003,text
LN:0004,text
LN:0005,text
LN:0006,text
```

## Example 1: output head

Outputs first 2 lines.

command line:
```text
cat file1.txt | aki-unbody --head 2
```

result output:
```text
LN:0001,text
LN:0002,text
```

## Example 2: output tail

Outputs last 2 lines.

command line:
```text
cat file1.txt | aki-unbody --tail 2
```

result output:
```text
LN:0005,text
LN:0006,text
```

## Example 3: output head and tail

Outputs first 2 lines and last 2 lines.

command line:
```text
cat file1.txt | aki-unbody --head 2 --tail 2
```

result output:
```text
LN:0001,text
LN:0002,text
LN:0005,text
LN:0006,text
```

## Example 4: output body, except for head and tail

Outputs body, except for first 2 lines and last 2 lines.

command line:
```text
cat file1.txt | aki-unbody --head 2 --tail 2 --inverse
```

result output:
```text
LN:0003,text
LN:0004,text
```

# Library example

See [`fn execute()`] for this library examples.

[`fn execute()`]: crate::execute
*/
#[macro_use]
extern crate anyhow;

mod conf;
mod run;
mod util;

use flood_tide::HelpVersion;
use runnel::RunnelIoe;
use std::io::Write;

const TRY_HELP_MSG: &str = "Try --help for help.";

/// execute unbody
///
/// params:
///   - sioe: stream in/out/err
///   - program: program name. etc. "unbody"
///   - args: parameter arguments.
///
/// return:
///   - ok: ()
///   - err: anyhow
///
/// # Examples
///
/// ## Example 1: output head
///
/// Outputs first 2 lines.
///
/// ```rust
/// use runnel::RunnelIoeBuilder;
///
/// let r = libaki_unbody::execute(&RunnelIoeBuilder::new().build(),
///     "unbody", &["--head", "2"]);
/// ```
///
/// ## Example 2: output tail
///
/// Outputs last 2 lines.
///
/// ```rust
/// use runnel::RunnelIoeBuilder;
///
/// let r = libaki_unbody::execute(&RunnelIoeBuilder::new().build(),
///     "unbody", &["--tail", "2"]);
/// ```
///
/// ## Example 3: output head and tail
///
/// Outputs first 2 lines and last 2 lines.
///
/// ```rust
/// use runnel::RunnelIoeBuilder;
///
/// let r = libaki_unbody::execute(&RunnelIoeBuilder::new().build(),
///     "unbody", &["--head", "2", "--tail", "2"]);
/// ```
///
/// ## Example 4: output body, except for head and tail
///
/// Outputs body, except for first 2 lines and last 2 lines.
///
/// ```rust
/// use runnel::RunnelIoeBuilder;
///
/// let r = libaki_unbody::execute(&RunnelIoeBuilder::new().build(),
///     "unbody", &["--head", "2", "--tail", "2", "--inverse"]);
/// ```
///
pub fn execute(sioe: &RunnelIoe, prog_name: &str, args: &[&str]) -> anyhow::Result<()> {
    let conf = match conf::parse_cmdopts(prog_name, args) {
        Ok(conf) => conf,
        Err(errs) => {
            for err in errs.iter().take(1) {
                if err.is_help() || err.is_version() {
                    let _r = sioe.pout().lock().write_fmt(format_args!("{err}\n"));
                    return Ok(());
                }
            }
            return Err(anyhow!("{}\n{}", errs, TRY_HELP_MSG));
        }
    };
    run::run(sioe, &conf)
}