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use anyhow::anyhow;

use radicle::git;
use radicle::git::raw::Oid;
use radicle::prelude::*;
use radicle::storage::git::Repository;

use crate::terminal as term;

/// Give the oid of the branch or an appropriate error.
#[inline]
pub fn branch_oid(branch: &git::raw::Branch) -> anyhow::Result<git::Oid> {
    let oid = branch
        .get()
        .target()
        .ok_or(anyhow!("invalid HEAD ref; aborting"))?;
    Ok(oid.into())
}

#[inline]
fn get_branch(git_ref: git::Qualified) -> git::RefString {
    let (_, _, head, tail) = git_ref.non_empty_components();
    std::iter::once(head).chain(tail).collect()
}

/// Determine the merge target for this patch. This can be any followed remote's "default" branch,
/// as well as your own (eg. `rad/master`).
pub fn get_merge_target(
    storage: &Repository,
    head_branch: &git::raw::Branch,
) -> anyhow::Result<(git::RefString, git::Oid)> {
    let (qualified_ref, target_oid) = storage.canonical_head()?;
    let head_oid = branch_oid(head_branch)?;
    let merge_base = storage.raw().merge_base(*head_oid, *target_oid)?;

    if head_oid == merge_base.into() {
        anyhow::bail!("commits are already included in the target branch; nothing to do");
    }

    Ok((get_branch(qualified_ref), (*target_oid).into()))
}

/// Get the diff stats between two commits.
/// Should match the default output of `git diff <old> <new> --stat` exactly.
pub fn diff_stats(
    repo: &git::raw::Repository,
    old: &Oid,
    new: &Oid,
) -> Result<git::raw::DiffStats, git::raw::Error> {
    let old = repo.find_commit(*old)?;
    let new = repo.find_commit(*new)?;
    let old_tree = old.tree()?;
    let new_tree = new.tree()?;
    let mut diff = repo.diff_tree_to_tree(Some(&old_tree), Some(&new_tree), None)?;
    let mut find_opts = git::raw::DiffFindOptions::new();

    diff.find_similar(Some(&mut find_opts))?;
    diff.stats()
}

/// Create a human friendly message about git's sync status.
pub fn ahead_behind(
    repo: &git::raw::Repository,
    revision_oid: Oid,
    head_oid: Oid,
) -> anyhow::Result<term::Line> {
    let (a, b) = repo.graph_ahead_behind(revision_oid, head_oid)?;
    if a == 0 && b == 0 {
        return Ok(term::Line::new(term::format::dim("up to date")));
    }

    let ahead = term::format::positive(a);
    let behind = term::format::negative(b);

    Ok(term::Line::default()
        .item("ahead ")
        .item(ahead)
        .item(", behind ")
        .item(behind))
}

/// Get the branches that point to a commit.
pub fn branches(target: &Oid, repo: &git::raw::Repository) -> anyhow::Result<Vec<String>> {
    let mut branches: Vec<String> = vec![];

    for r in repo.references()?.flatten() {
        if !r.is_branch() {
            continue;
        }
        if let (Some(oid), Some(name)) = (&r.target(), &r.shorthand()) {
            if oid == target {
                branches.push(name.to_string());
            };
        };
    }
    Ok(branches)
}

#[inline]
pub fn try_branch(reference: git::raw::Reference<'_>) -> anyhow::Result<git::raw::Branch> {
    let branch = if reference.is_branch() {
        git::raw::Branch::wrap(reference)
    } else {
        anyhow::bail!("cannot create patch from detached head; aborting")
    };
    Ok(branch)
}