use std::process::Command;
use unicode_segmentation::UnicodeSegmentation;

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

use crate::configs::hg_branch::HgBranchConfig;

/// 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_files(&[".hgignore"])
        .set_folders(&[".hg"])
        .is_match();

    if !is_hg_repo {
        return None;
    }

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

    module.get_prefix().set_value("on ");

    let truncation_symbol = get_graphemes(config.truncation_symbol, 1);
    module.create_segment("symbol", &config.symbol);

    // 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 get_branch_name = |tmpl| get_hg_log_template(tmpl, context);

    let branch_name = get_branch_name("{activebookmark}")
        .or_else(|| get_branch_name("{branch}"))
        .unwrap_or_else(|| "(no branch)".to_string());

    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) {
        truncated_graphemes + &truncation_symbol
    } else {
        truncated_graphemes
    };

    module.create_segment(
        "name",
        &config.branch_name.with_value(&truncated_and_symbol),
    );

    Some(module)
}

fn get_hg_log_template(hgtmpl: &str, ctx: &Context) -> Option<String> {
    let output = Command::new("hg")
        .args(&["log", "-r", ".", "--template", hgtmpl])
        .current_dir(&ctx.current_dir)
        .output()
        .ok()
        .and_then(|output| String::from_utf8(output.stdout).ok())?;

    if output.is_empty() {
        None
    } else {
        Some(output)
    }
}

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()
}