use anyhow::Result;
use collections::HashMap;
use parking_lot::Mutex;
use std::{
    path::{Component, Path, PathBuf},
    sync::Arc,
};

pub use git2::Repository as LibGitRepository;

#[async_trait::async_trait]
pub trait GitRepository: Send {
    fn reload_index(&self);

    fn load_index_text(&self, relative_file_path: &Path) -> Option<String>;
}

#[async_trait::async_trait]
impl GitRepository for LibGitRepository {
    fn reload_index(&self) {
        if let Ok(mut index) = self.index() {
            _ = index.read(false);
        }
    }

    fn load_index_text(&self, relative_file_path: &Path) -> Option<String> {
        fn logic(repo: &LibGitRepository, relative_file_path: &Path) -> Result<Option<String>> {
            const STAGE_NORMAL: i32 = 0;
            let index = repo.index()?;

            // This check is required because index.get_path() unwraps internally :(
            check_path_to_repo_path_errors(relative_file_path)?;

            let oid = match index.get_path(&relative_file_path, STAGE_NORMAL) {
                Some(entry) => entry.id,
                None => return Ok(None),
            };

            let content = repo.find_blob(oid)?.content().to_owned();
            Ok(Some(String::from_utf8(content)?))
        }

        match logic(&self, relative_file_path) {
            Ok(value) => return value,
            Err(err) => log::error!("Error loading head text: {:?}", err),
        }
        None
    }
}

#[derive(Debug, Clone, Default)]
pub struct FakeGitRepository {
    state: Arc<Mutex<FakeGitRepositoryState>>,
}

#[derive(Debug, Clone, Default)]
pub struct FakeGitRepositoryState {
    pub index_contents: HashMap<PathBuf, String>,
}

impl FakeGitRepository {
    pub fn open(state: Arc<Mutex<FakeGitRepositoryState>>) -> Arc<Mutex<dyn GitRepository>> {
        Arc::new(Mutex::new(FakeGitRepository { state }))
    }
}

#[async_trait::async_trait]
impl GitRepository for FakeGitRepository {
    fn reload_index(&self) {}

    fn load_index_text(&self, path: &Path) -> Option<String> {
        let state = self.state.lock();
        state.index_contents.get(path).cloned()
    }
}

fn check_path_to_repo_path_errors(relative_file_path: &Path) -> Result<()> {
    match relative_file_path.components().next() {
        None => anyhow::bail!("repo path should not be empty"),
        Some(Component::Prefix(_)) => anyhow::bail!(
            "repo path `{}` should be relative, not a windows prefix",
            relative_file_path.to_string_lossy()
        ),
        Some(Component::RootDir) => {
            anyhow::bail!(
                "repo path `{}` should be relative",
                relative_file_path.to_string_lossy()
            )
        }
        Some(Component::CurDir) => {
            anyhow::bail!(
                "repo path `{}` should not start with `.`",
                relative_file_path.to_string_lossy()
            )
        }
        Some(Component::ParentDir) => {
            anyhow::bail!(
                "repo path `{}` should not start with `..`",
                relative_file_path.to_string_lossy()
            )
        }
        _ => Ok(()),
    }
}