use std::env;
use std::path::Path;
use git2::{ Repository, Status };
use colored::*;

pub fn vcs_status() -> Option<(colored::ColoredString, colored::ColoredString)> {
    let current_dir = env::var("PWD").unwrap();

    let mut repo: Option<Repository> = None;
    let current_path = Path::new(&current_dir[..]);
    for path in current_path.ancestors() {
        match Repository::open(path) {
            Ok(r) => {
                repo = Some(r);
                break;
            }
            Err(_) => {},
        }
    }
    if repo.is_none() {
        return None
    }
    let repo = repo.unwrap();

    let mut commit_dist: String = "".into();
    if let Some((ahead, behind)) = get_ahead_behind(&repo) {
        if ahead > 0 {
            commit_dist.push_str(" ↑");
        }
        if behind > 0 {
            commit_dist.push_str(" ↓");
        }
    }

    let reference = match repo.head() {
        Ok(r) => r,
        Err(_) => return None
    };
    let mut branch;

    let branch_color = env::var("BRANCH_COLOR").unwrap_or("bright black".into());
    let commit_color = env::var("COMMIT_COLOR").unwrap_or("bright black".into());

    if reference.is_branch() {
        branch = format!("{}{}", reference.shorthand().unwrap(), commit_dist).color(branch_color);
    } else {
        let commit = reference.peel_to_commit().unwrap();
        let id = commit.id();
        branch = format!("{:.6}{}", id, commit_dist).color(commit_color);
    }

    let git_clean_color          = env::var("GIT_CLEAN_COLOR").unwrap_or("green".into());
    let git_wt_modified_color    = env::var("GIT_WT_MODIFIED_COLOR").unwrap_or("red".into());
    let git_index_modified_color = env::var("GIT_INDEX_MODIFIED_COLOR").unwrap_or("yellow".into());
    let stat_char = env::var("GIT_CLEAN").unwrap_or("·".into());
    let mut repo_stat = stat_char.color(&git_clean_color[..]);

    let file_stats = repo.statuses(None).unwrap();
    for file in file_stats.iter() {
        match file.status() {
            // STATE: unstaged (working tree modified)
            Status::WT_NEW        | Status::WT_MODIFIED      |
            Status::WT_DELETED    | Status::WT_TYPECHANGE    |
            Status::WT_RENAMED => {
                let stat_char = env::var("GIT_WT_MODIFIED").unwrap_or("×".into());
                repo_stat = stat_char.color(&git_wt_modified_color[..]);
                break;
            },
            // STATE: staged (changes added to index)
            Status::INDEX_NEW     | Status::INDEX_MODIFIED   |
            Status::INDEX_DELETED | Status::INDEX_TYPECHANGE |
            Status::INDEX_RENAMED => {
                let stat_char = env::var("GIT_INDEX_MODIFIED").unwrap_or("±".into());
                repo_stat = stat_char.color(&git_index_modified_color[..]);
            },
            // STATE: committed (changes have been saved in the repo)
            _ => {
                let stat_char = env::var("GIT_CLEAN").unwrap_or("·".into());
                repo_stat = stat_char.color(&git_clean_color[..]);
            }
        }
    }
    return Some((branch, repo_stat))
}

fn get_ahead_behind(r: &Repository) -> Option<(usize, usize)> {
  let head = (r.head().ok())?;
  if !head.is_branch() {
    return None
  }

  let head_name    = (head.shorthand())?;
  let head_branch  = (r.find_branch(head_name, git2::BranchType::Local).ok())?;
  let upstream     = (head_branch.upstream().ok())?;
  let head_oid     = (head.target())?;
  let upstream_oid = (upstream.get().target())?;

  r.graph_ahead_behind(head_oid, upstream_oid).ok()
}