module help

import os

// Topics whose module uses the cli or flag modules (both support --help).
const cli_topics = ['new', 'init', 'repeat']

fn hdir(base string) string {
    return os.join_path(base, 'vlib', 'v', 'help')
}

fn help_dir() string {
    vexe := get_vexe()
    if vexe != '' {
        return hdir(os.dir(vexe))
    }
    // use @VEXEROOT, but only if everything else fails; the negative of using it,
    // is that it will depend on the filesystem of the host that built v
    return hdir(@VEXEROOT)
}

@[params]
pub struct ExitOptions {
pub:
    exit_code int
}

// print_and_exit prints the help topic and exits.
@[noreturn]
pub fn print_and_exit(topic string, opts ExitOptions) {
    if topic == 'topics' {
        print_known_topics()
        exit(opts.exit_code)
    }
    fail_code := if opts.exit_code != 0 { opts.exit_code } else { 1 }
    for c in topic {
        if !c.is_letter() && !c.is_digit() && c != `-` {
            print_topic_unknown(topic)
            exit(fail_code)
        }
    }
    if topic in cli_topics {
        vexe := get_vexe()
        os.system('${os.quoted_path(vexe)} ${topic} --help')
        exit(opts.exit_code)
    }
    mut topic_path := ''
    for path in os.walk_ext(help_dir(), '.txt') {
        if topic == os.file_name(path).all_before('.txt') {
            topic_path = path
            break
        }
    }
    if topic_path == '' {
        print_topic_unknown(topic)
        print_known_topics()
        exit(fail_code)
    }
    topic_content := os.read_file(topic_path) or {
        msg := err.str()
        eprintln('error: failed reading topic file: ${msg}')
        exit(fail_code)
    }
    cleaned := topic_content.trim_space()
    println(cleaned)
    exit(opts.exit_code)
}

fn print_topic_unknown(topic string) {
    eprintln('error: unknown help topic "${topic}". Use `v help` for usage information.')
}

fn print_known_topics() {
    topic_paths := os.walk_ext(help_dir(), '.txt')
    mut res := []string{}
    for path in topic_paths {
        topic := os.file_name(path).all_before('.txt')
        if topic != 'default' {
            res << topic
        }
    }
    sorted_topics := res.sorted()
    println('Known help topics: ${sorted_topics}')
}

fn get_vexe() string {
    mut vexe := os.getenv('VEXE')
    if vexe == '' {
        vexe = os.executable()
    }
    return vexe
}