//! `koh man` — the manual, built into the binary.
//!
//! The page lives in `docs/koh3-man.txt` and is embedded at build time, so a
//! `koh` copied to another machine still carries its own documentation. With a
//! command name it prints just that command's part; otherwise the whole page,
//! through the pager on a terminal.

module cli

import os
import src.fmt

const manual = $embed_file('../../docs/koh3-man.txt').to_string()

pub fn cmd_man(raw []string) int {
	args := parse('man', raw, Options{}) or { return usage_error(err.msg()) }
	mut text := manual
	if args.positional.len > 0 {
		name := args.positional_at(0)
		text = section_of(name) or {
			eprintln('  ${fmt.red(fmt.glyph_fail)} the manual has no "${name}" — try "koh man" for the whole page')
			return 2
		}
	}
	page(text)
	return 0
}

// section_of returns the part of the COMMANDS section that documents one
// command: from its synopsis to the next command's.
fn section_of(name string) ?string {
	lines := manual.split_into_lines()
	mut start := -1
	for i, line in lines {
		if line.starts_with('    koh ') && line.contains(' ${name}') {
			start = i
			break
		}
	}
	if start < 0 {
		return none
	}
	mut end := lines.len
	for i := start + 1; i < lines.len; i++ {
		trimmed := lines[i].trim_space()
		if trimmed.starts_with('koh ') && lines[i].starts_with('    ') {
			end = i
			break
		}
		if lines[i].starts_with('OPTIONS') || lines[i].starts_with('ENVIRONMENT') {
			end = i
			break
		}
	}
	return lines[start..end].join('\n')
}

// page hands the text to the pager on a terminal, and prints it plainly when
// the output is going somewhere else. The pager gets a temporary file because
// that is the one interface every pager understands.
fn page(text string) {
	pager := os.getenv('PAGER')
	if os.is_atty(1) != 0 && pager != '' {
		path := os.join_path(os.temp_dir(), 'koh-man-${os.getpid()}.txt')
		os.write_file(path, text) or {
			print(text)
			return
		}
		// The path is one we built from the temp dir and our own pid, so it
		// carries nothing the shell could interpret.
		os.execute('${pager} ${path}')
		os.rm(path) or {}
		return
	}
	print(text)
	if !text.ends_with('\n') {
		println('')
	}
}