// Copyright 2021 The Jujutsu Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#![allow(missing_docs)]

use std::collections::HashMap;
use std::fs;
use std::fs::File;
use std::io::{self, Write};
use std::path::{Path, PathBuf};
use std::sync::Arc;

use thiserror::Error;

use crate::backend::{Backend, BackendInitError, MergedTreeId};
use crate::commit::Commit;
use crate::file_util::{self, IoResultExt as _, PathError};
use crate::git_backend::{canonicalize_git_repo_path, GitBackend};
use crate::local_backend::LocalBackend;
use crate::local_working_copy::LocalWorkingCopy;
use crate::op_store::{OperationId, WorkspaceId};
use crate::repo::{
    read_store_type_compat, BackendInitializer, CheckOutCommitError, IndexStoreInitializer,
    OpHeadsStoreInitializer, OpStoreInitializer, ReadonlyRepo, Repo, RepoInitError, RepoLoader,
    StoreFactories, StoreLoadError, SubmoduleStoreInitializer,
};
use crate::settings::UserSettings;
use crate::signing::{SignInitError, Signer};
use crate::store::Store;
use crate::working_copy::{
    CheckoutError, CheckoutStats, LockedWorkingCopy, WorkingCopy, WorkingCopyStateError,
};

#[derive(Error, Debug)]
pub enum WorkspaceInitError {
    #[error("The destination repo ({0}) already exists")]
    DestinationExists(PathBuf),
    #[error("Repo path could not be interpreted as Unicode text")]
    NonUnicodePath,
    #[error(transparent)]
    CheckOutCommit(#[from] CheckOutCommitError),
    #[error(transparent)]
    WorkingCopyState(#[from] WorkingCopyStateError),
    #[error(transparent)]
    Path(#[from] PathError),
    #[error(transparent)]
    Backend(#[from] BackendInitError),
    #[error(transparent)]
    SignInit(#[from] SignInitError),
}

#[derive(Error, Debug)]
pub enum WorkspaceLoadError {
    #[error("The repo appears to no longer be at {0}")]
    RepoDoesNotExist(PathBuf),
    #[error("There is no Jujutsu repo in {0}")]
    NoWorkspaceHere(PathBuf),
    #[error("Cannot read the repo: {0}")]
    StoreLoadError(#[from] StoreLoadError),
    #[error("Repo path could not be interpreted as Unicode text")]
    NonUnicodePath,
    #[error(transparent)]
    Path(#[from] PathError),
}

/// Represents a workspace, i.e. what's typically the .jj/ directory and its
/// parent.
pub struct Workspace {
    // Path to the workspace root (typically the parent of a .jj/ directory), which is where
    // working copy files live.
    workspace_root: PathBuf,
    repo_loader: RepoLoader,
    working_copy: Box<dyn WorkingCopy>,
}

fn create_jj_dir(workspace_root: &Path) -> Result<PathBuf, WorkspaceInitError> {
    let jj_dir = workspace_root.join(".jj");
    match std::fs::create_dir(&jj_dir).context(&jj_dir) {
        Ok(()) => Ok(jj_dir),
        Err(ref e) if e.error.kind() == io::ErrorKind::AlreadyExists => {
            Err(WorkspaceInitError::DestinationExists(jj_dir))
        }
        Err(e) => Err(e.into()),
    }
}

fn init_working_copy(
    user_settings: &UserSettings,
    repo: &Arc<ReadonlyRepo>,
    workspace_root: &Path,
    jj_dir: &Path,
    working_copy_initializer: &WorkingCopyInitializer,
    workspace_id: WorkspaceId,
) -> Result<(Box<dyn WorkingCopy>, Arc<ReadonlyRepo>), WorkspaceInitError> {
    let working_copy_state_path = jj_dir.join("working_copy");
    std::fs::create_dir(&working_copy_state_path).context(&working_copy_state_path)?;

    let mut tx = repo.start_transaction(user_settings);
    tx.mut_repo().check_out(
        workspace_id.clone(),
        user_settings,
        &repo.store().root_commit(),
    )?;
    let repo = tx.commit(format!("add workspace '{}'", workspace_id.as_str()));

    let working_copy = working_copy_initializer(
        repo.store().clone(),
        workspace_root.to_path_buf(),
        working_copy_state_path.clone(),
        workspace_id,
        repo.op_id().clone(),
    )?;
    let working_copy_type_path = working_copy_state_path.join("type");
    fs::write(&working_copy_type_path, working_copy.name()).context(&working_copy_type_path)?;
    Ok((working_copy, repo))
}

impl Workspace {
    fn new(
        workspace_root: &Path,
        working_copy: Box<dyn WorkingCopy>,
        repo_loader: RepoLoader,
    ) -> Result<Workspace, PathError> {
        let workspace_root = workspace_root.canonicalize().context(workspace_root)?;
        Ok(Workspace {
            workspace_root,
            repo_loader,
            working_copy,
        })
    }

    pub fn init_local(
        user_settings: &UserSettings,
        workspace_root: &Path,
    ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
        let backend_initializer: &BackendInitializer =
            &|_settings, store_path| Ok(Box::new(LocalBackend::init(store_path)));
        let signer = Signer::from_settings(user_settings)?;
        Self::init_with_backend(user_settings, workspace_root, backend_initializer, signer)
    }

    /// Initializes a workspace with a new Git backend and bare Git repo in
    /// `.jj/repo/store/git`.
    pub fn init_internal_git(
        user_settings: &UserSettings,
        workspace_root: &Path,
    ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
        let backend_initializer: &BackendInitializer =
            &|settings, store_path| Ok(Box::new(GitBackend::init_internal(settings, store_path)?));
        let signer = Signer::from_settings(user_settings)?;
        Self::init_with_backend(user_settings, workspace_root, backend_initializer, signer)
    }

    /// Initializes a workspace with a new Git backend and Git repo that shares
    /// the same working copy.
    pub fn init_colocated_git(
        user_settings: &UserSettings,
        workspace_root: &Path,
    ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
        let backend_initializer = |settings: &UserSettings,
                                   store_path: &Path|
         -> Result<Box<dyn Backend>, _> {
            // TODO: Clean up path normalization. store_path is canonicalized by
            // ReadonlyRepo::init(). workspace_root will be canonicalized by
            // Workspace::new(), but it's not yet here.
            let store_relative_workspace_root =
                if let Ok(workspace_root) = workspace_root.canonicalize() {
                    file_util::relative_path(store_path, &workspace_root)
                } else {
                    workspace_root.to_owned()
                };
            let backend =
                GitBackend::init_colocated(settings, store_path, &store_relative_workspace_root)?;
            Ok(Box::new(backend))
        };
        let signer = Signer::from_settings(user_settings)?;
        Self::init_with_backend(user_settings, workspace_root, &backend_initializer, signer)
    }

    /// Initializes a workspace with an existing Git repo at the specified path.
    pub fn init_external_git(
        user_settings: &UserSettings,
        workspace_root: &Path,
        git_repo_path: &Path,
    ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
        let backend_initializer =
            |settings: &UserSettings, store_path: &Path| -> Result<Box<dyn Backend>, _> {
                // If the git repo is inside the workspace, use a relative path to it so the
                // whole workspace can be moved without breaking.
                // TODO: Clean up path normalization. store_path is canonicalized by
                // ReadonlyRepo::init(). workspace_root will be canonicalized by
                // Workspace::new(), but it's not yet here.
                let store_relative_git_repo_path = match (
                    workspace_root.canonicalize(),
                    canonicalize_git_repo_path(git_repo_path),
                ) {
                    (Ok(workspace_root), Ok(git_repo_path))
                        if git_repo_path.starts_with(&workspace_root) =>
                    {
                        file_util::relative_path(store_path, &git_repo_path)
                    }
                    _ => git_repo_path.to_owned(),
                };
                let backend =
                    GitBackend::init_external(settings, store_path, &store_relative_git_repo_path)?;
                Ok(Box::new(backend))
            };
        let signer = Signer::from_settings(user_settings)?;
        Self::init_with_backend(user_settings, workspace_root, &backend_initializer, signer)
    }

    #[allow(clippy::too_many_arguments)]
    pub fn init_with_factories(
        user_settings: &UserSettings,
        workspace_root: &Path,
        backend_initializer: &BackendInitializer,
        signer: Signer,
        op_store_initializer: &OpStoreInitializer,
        op_heads_store_initializer: &OpHeadsStoreInitializer,
        index_store_initializer: &IndexStoreInitializer,
        submodule_store_initializer: &SubmoduleStoreInitializer,
        working_copy_initializer: &WorkingCopyInitializer,
        workspace_id: WorkspaceId,
    ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
        let jj_dir = create_jj_dir(workspace_root)?;
        (|| {
            let repo_dir = jj_dir.join("repo");
            std::fs::create_dir(&repo_dir).context(&repo_dir)?;
            let repo = ReadonlyRepo::init(
                user_settings,
                &repo_dir,
                backend_initializer,
                signer,
                op_store_initializer,
                op_heads_store_initializer,
                index_store_initializer,
                submodule_store_initializer,
            )
            .map_err(|repo_init_err| match repo_init_err {
                RepoInitError::Backend(err) => WorkspaceInitError::Backend(err),
                RepoInitError::Path(err) => WorkspaceInitError::Path(err),
            })?;
            let (working_copy, repo) = init_working_copy(
                user_settings,
                &repo,
                workspace_root,
                &jj_dir,
                working_copy_initializer,
                workspace_id,
            )?;
            let repo_loader = repo.loader();
            let workspace = Workspace::new(workspace_root, working_copy, repo_loader)?;
            Ok((workspace, repo))
        })()
        .map_err(|err| {
            let _ = std::fs::remove_dir_all(jj_dir);
            err
        })
    }

    pub fn init_with_backend(
        user_settings: &UserSettings,
        workspace_root: &Path,
        backend_initializer: &BackendInitializer,
        signer: Signer,
    ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
        Self::init_with_factories(
            user_settings,
            workspace_root,
            backend_initializer,
            signer,
            ReadonlyRepo::default_op_store_initializer(),
            ReadonlyRepo::default_op_heads_store_initializer(),
            ReadonlyRepo::default_index_store_initializer(),
            ReadonlyRepo::default_submodule_store_initializer(),
            default_working_copy_initializer(),
            WorkspaceId::default(),
        )
    }

    pub fn init_workspace_with_existing_repo(
        user_settings: &UserSettings,
        workspace_root: &Path,
        repo: &Arc<ReadonlyRepo>,
        working_copy_initializer: &WorkingCopyInitializer,
        workspace_id: WorkspaceId,
    ) -> Result<(Self, Arc<ReadonlyRepo>), WorkspaceInitError> {
        let jj_dir = create_jj_dir(workspace_root)?;

        let repo_dir = repo.repo_path().canonicalize().context(repo.repo_path())?;
        let repo_file_path = jj_dir.join("repo");
        let mut repo_file = File::create(&repo_file_path).context(&repo_file_path)?;
        repo_file
            .write_all(
                repo_dir
                    .to_str()
                    .ok_or(WorkspaceInitError::NonUnicodePath)?
                    .as_bytes(),
            )
            .context(&repo_file_path)?;

        let (working_copy, repo) = init_working_copy(
            user_settings,
            repo,
            workspace_root,
            &jj_dir,
            working_copy_initializer,
            workspace_id,
        )?;
        let workspace = Workspace::new(workspace_root, working_copy, repo.loader())?;
        Ok((workspace, repo))
    }

    pub fn load(
        user_settings: &UserSettings,
        workspace_path: &Path,
        store_factories: &StoreFactories,
        working_copy_factories: &HashMap<String, WorkingCopyFactory>,
    ) -> Result<Self, WorkspaceLoadError> {
        let loader = WorkspaceLoader::init(workspace_path)?;
        let workspace = loader.load(user_settings, store_factories, working_copy_factories)?;
        Ok(workspace)
    }

    pub fn workspace_root(&self) -> &PathBuf {
        &self.workspace_root
    }

    pub fn workspace_id(&self) -> &WorkspaceId {
        self.working_copy.workspace_id()
    }

    pub fn repo_path(&self) -> &PathBuf {
        self.repo_loader.repo_path()
    }

    pub fn repo_loader(&self) -> &RepoLoader {
        &self.repo_loader
    }

    pub fn working_copy(&self) -> &dyn WorkingCopy {
        self.working_copy.as_ref()
    }

    pub fn start_working_copy_mutation(
        &mut self,
    ) -> Result<LockedWorkspace, WorkingCopyStateError> {
        let locked_wc = self.working_copy.start_mutation()?;
        Ok(LockedWorkspace {
            base: self,
            locked_wc,
        })
    }

    pub fn check_out(
        &mut self,
        operation_id: OperationId,
        old_tree_id: Option<&MergedTreeId>,
        commit: &Commit,
    ) -> Result<CheckoutStats, CheckoutError> {
        let mut locked_ws =
            self.start_working_copy_mutation()
                .map_err(|err| CheckoutError::Other {
                    message: "Failed to start editing the working copy state".to_string(),
                    err: err.into(),
                })?;
        // Check if the current working-copy commit has changed on disk compared to what
        // the caller expected. It's safe to check out another commit
        // regardless, but it's probably not what  the caller wanted, so we let
        // them know.
        if let Some(old_tree_id) = old_tree_id {
            if old_tree_id != locked_ws.locked_wc().old_tree_id() {
                return Err(CheckoutError::ConcurrentCheckout);
            }
        }
        let stats = locked_ws.locked_wc().check_out(commit)?;
        locked_ws
            .finish(operation_id)
            .map_err(|err| CheckoutError::Other {
                message: "Failed to save the working copy state".to_string(),
                err: err.into(),
            })?;
        Ok(stats)
    }
}

pub struct LockedWorkspace<'a> {
    base: &'a mut Workspace,
    locked_wc: Box<dyn LockedWorkingCopy>,
}

impl<'a> LockedWorkspace<'a> {
    pub fn locked_wc(&mut self) -> &mut dyn LockedWorkingCopy {
        self.locked_wc.as_mut()
    }

    pub fn finish(self, operation_id: OperationId) -> Result<(), WorkingCopyStateError> {
        let new_wc = self.locked_wc.finish(operation_id)?;
        self.base.working_copy = new_wc;
        Ok(())
    }
}

#[derive(Clone, Debug)]
pub struct WorkspaceLoader {
    workspace_root: PathBuf,
    repo_dir: PathBuf,
    working_copy_state_path: PathBuf,
}

impl WorkspaceLoader {
    pub fn init(workspace_root: &Path) -> Result<Self, WorkspaceLoadError> {
        let jj_dir = workspace_root.join(".jj");
        if !jj_dir.is_dir() {
            return Err(WorkspaceLoadError::NoWorkspaceHere(
                workspace_root.to_owned(),
            ));
        }
        let mut repo_dir = jj_dir.join("repo");
        // If .jj/repo is a file, then we interpret its contents as a relative path to
        // the actual repo directory (typically in another workspace).
        if repo_dir.is_file() {
            let buf = fs::read(&repo_dir).context(&repo_dir)?;
            let repo_path_str =
                String::from_utf8(buf).map_err(|_| WorkspaceLoadError::NonUnicodePath)?;
            repo_dir = jj_dir
                .join(&repo_path_str)
                .canonicalize()
                .context(&repo_path_str)?;
            if !repo_dir.is_dir() {
                return Err(WorkspaceLoadError::RepoDoesNotExist(repo_dir));
            }
        }
        let working_copy_state_path = jj_dir.join("working_copy");
        Ok(WorkspaceLoader {
            workspace_root: workspace_root.to_owned(),
            repo_dir,
            working_copy_state_path,
        })
    }

    pub fn workspace_root(&self) -> &Path {
        &self.workspace_root
    }

    pub fn repo_path(&self) -> &Path {
        &self.repo_dir
    }

    pub fn load(
        &self,
        user_settings: &UserSettings,
        store_factories: &StoreFactories,
        working_copy_factories: &HashMap<String, WorkingCopyFactory>,
    ) -> Result<Workspace, WorkspaceLoadError> {
        let repo_loader = RepoLoader::init(user_settings, &self.repo_dir, store_factories)?;
        let working_copy = self.load_working_copy(repo_loader.store(), working_copy_factories)?;
        let workspace = Workspace::new(&self.workspace_root, working_copy, repo_loader)?;
        Ok(workspace)
    }

    fn load_working_copy(
        &self,
        store: &Arc<Store>,
        working_copy_factories: &HashMap<String, WorkingCopyFactory>,
    ) -> Result<Box<dyn WorkingCopy>, StoreLoadError> {
        // For compatibility with existing repos. TODO: Delete default in 0.17+
        let working_copy_type = read_store_type_compat(
            "working copy",
            self.working_copy_state_path.join("type"),
            LocalWorkingCopy::name,
        )?;
        let working_copy_factory =
            working_copy_factories
                .get(&working_copy_type)
                .ok_or_else(|| StoreLoadError::UnsupportedType {
                    store: "working copy",
                    store_type: working_copy_type.to_string(),
                })?;
        let working_copy =
            working_copy_factory(store, &self.workspace_root, &self.working_copy_state_path);
        Ok(working_copy)
    }
}

pub fn default_working_copy_initializer() -> &'static WorkingCopyInitializer<'static> {
    &|store: Arc<Store>, working_copy_path, state_path, workspace_id, operation_id| {
        let wc = LocalWorkingCopy::init(
            store,
            working_copy_path,
            state_path,
            operation_id,
            workspace_id,
        )?;
        Ok(Box::new(wc))
    }
}

pub fn default_working_copy_factories() -> HashMap<String, WorkingCopyFactory> {
    let mut factories: HashMap<String, WorkingCopyFactory> = HashMap::new();
    factories.insert(
        LocalWorkingCopy::name().to_owned(),
        Box::new(|store, working_copy_path, store_path| {
            Box::new(LocalWorkingCopy::load(
                store.clone(),
                working_copy_path.to_owned(),
                store_path.to_owned(),
            ))
        }),
    );
    factories
}

pub type WorkingCopyInitializer<'a> = dyn Fn(
        Arc<Store>,
        PathBuf,
        PathBuf,
        WorkspaceId,
        OperationId,
    ) -> Result<Box<dyn WorkingCopy>, WorkingCopyStateError>
    + 'a;
pub type WorkingCopyFactory = Box<dyn Fn(&Arc<Store>, &Path, &Path) -> Box<dyn WorkingCopy>>;