starship/src/modules/hg_branch.rs

use unicode_segmentation::UnicodeSegmentation;

use super::{Context, Module, RootModuleConfig};

use crate::configs::hg_branch::HgBranchConfig;
use crate::formatter::StringFormatter;

/// Creates a module with the Hg bookmark or branch in the current directory
///
/// Will display the bookmark or branch name if the current directory is an hg repo
pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
    let is_hg_repo = context.try_begin_scan()?.set_folders(&[".hg"]).is_match();

    if !is_hg_repo {
        return None;
    }

    let mut module = context.new_module("hg_branch");
    let config: HgBranchConfig = HgBranchConfig::try_load(module.config);

    // TODO: Once error handling is implemented, warn the user if their config
    // truncation length is nonsensical
    let len = if config.truncation_length <= 0 {
        log::warn!(
            "\"truncation_length\" should be a positive value, found {}",
            config.truncation_length
        );
        std::usize::MAX
    } else {
        config.truncation_length as usize
    };

    let branch_name =
        get_hg_current_bookmark(context).unwrap_or_else(|| get_hg_branch_name(context));

    let truncated_graphemes = get_graphemes(&branch_name, len);
    // The truncation symbol should only be added if we truncated
    let truncated_and_symbol = if len < graphemes_len(&branch_name) {
        let truncation_symbol = get_graphemes(config.truncation_symbol, 1);
        truncated_graphemes + &truncation_symbol
    } else {
        truncated_graphemes
    };

    let parsed = StringFormatter::new(config.format).and_then(|formatter| {
        formatter
            .map_meta(|variable, _| match variable {
                "symbol" => Some(config.symbol),
                _ => None,
            })
            .map_style(|variable| match variable {
                "style" => Some(Ok(config.style)),
                _ => None,
            })
            .map(|variable| match variable {
                "branch" => Some(Ok(truncated_and_symbol.as_str())),
                _ => None,
            })
            .parse(None)
    });

    module.set_segments(match parsed {
        Ok(segments) => segments,
        Err(error) => {
            log::warn!("Error in module `hg_branch`:\n{}", error);
            return None;
        }
    });

    Some(module)
}

fn get_hg_branch_name(ctx: &Context) -> String {
    std::fs::read_to_string(ctx.current_dir.join(".hg").join("branch"))
        .map(|s| s.trim().into())
        .unwrap_or_else(|_| "default".to_string())
}

fn get_hg_current_bookmark(ctx: &Context) -> Option<String> {
    std::fs::read_to_string(ctx.current_dir.join(".hg").join("bookmarks.current"))
        .map(|s| s.trim().into())
        .ok()
}

fn get_graphemes(text: &str, length: usize) -> String {
    UnicodeSegmentation::graphemes(text, true)
        .take(length)
        .collect::<Vec<&str>>()
        .concat()
}

fn graphemes_len(text: &str) -> usize {
    UnicodeSegmentation::graphemes(&text[..], true).count()
}