// Copyright 2020 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.

use tracing::instrument;

use crate::cli_util::{print_unmatched_explicit_paths, CommandHelper, RevisionArg};
use crate::command_error::CommandError;
use crate::diff_util::DiffFormatArgs;
use crate::ui::Ui;

/// Compare file contents between two revisions
///
/// With the `-r` option, which is the default, shows the changes compared to
/// the parent revision. If there are several parent revisions (i.e., the given
/// revision is a merge), then they will be merged and the changes from the
/// result to the given revision will be shown.
///
/// With the `--from` and/or `--to` options, shows the difference from/to the
/// given revisions. If either is left out, it defaults to the working-copy
/// commit. For example, `jj diff --from main` shows the changes from "main"
/// (perhaps a branch name) to the working-copy commit.
#[derive(clap::Args, Clone, Debug)]
pub(crate) struct DiffArgs {
    /// Show changes in this revision, compared to its parent(s)
    ///
    /// If the revision is a merge commit, this shows changes *from* the
    /// automatic merge of the contents of all of its parents *to* the contents
    /// of the revision itself.
    #[arg(long, short)]
    revision: Option<RevisionArg>,
    /// Show changes from this revision
    #[arg(long, conflicts_with = "revision")]
    from: Option<RevisionArg>,
    /// Show changes to this revision
    #[arg(long, conflicts_with = "revision")]
    to: Option<RevisionArg>,
    /// Restrict the diff to these paths
    #[arg(value_hint = clap::ValueHint::AnyPath)]
    paths: Vec<String>,
    #[command(flatten)]
    format: DiffFormatArgs,
}

#[instrument(skip_all)]
pub(crate) fn cmd_diff(
    ui: &mut Ui,
    command: &CommandHelper,
    args: &DiffArgs,
) -> Result<(), CommandError> {
    let workspace_command = command.workspace_helper(ui)?;
    let from_tree;
    let to_tree;
    if args.from.is_some() || args.to.is_some() {
        let from =
            workspace_command.resolve_single_rev(args.from.as_ref().unwrap_or(&RevisionArg::AT))?;
        from_tree = from.tree()?;
        let to =
            workspace_command.resolve_single_rev(args.to.as_ref().unwrap_or(&RevisionArg::AT))?;
        to_tree = to.tree()?;
    } else {
        let commit = workspace_command
            .resolve_single_rev(args.revision.as_ref().unwrap_or(&RevisionArg::AT))?;
        from_tree = commit.parent_tree(workspace_command.repo().as_ref())?;
        to_tree = commit.tree()?
    }
    let fileset_expression = workspace_command.parse_file_patterns(&args.paths)?;
    let matcher = fileset_expression.to_matcher();
    let diff_renderer = workspace_command.diff_renderer_for(&args.format)?;
    ui.request_pager();
    diff_renderer.show_diff(
        ui,
        ui.stdout_formatter().as_mut(),
        &from_tree,
        &to_tree,
        matcher.as_ref(),
    )?;
    print_unmatched_explicit_paths(
        ui,
        &workspace_command,
        &fileset_expression,
        [&from_tree, &to_tree],
    )?;
    Ok(())
}