// Copyright 2024 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 clap_complete::ArgValueCompleter;
use jj_lib::absorb::AbsorbSource;
use jj_lib::absorb::absorb_hunks;
use jj_lib::absorb::split_hunks_to_trees;
use jj_lib::matchers::EverythingMatcher;
use tracing::instrument;

use crate::cli_util::CommandHelper;
use crate::cli_util::RevisionArg;
use crate::cli_util::print_unmatched_explicit_paths;
use crate::cli_util::print_updated_commits;
use crate::command_error::CommandError;
use crate::complete;
use crate::diff_util::DiffFormat;
use crate::ui::Ui;

/// Move changes from a revision into the stack of mutable revisions
///
/// This command splits changes in the source revision and moves each change to
/// the closest mutable ancestor where the corresponding lines were modified
/// last. If the destination revision cannot be determined unambiguously, the
/// change will be left in the source revision.
///
/// The source revision will be abandoned if all changes are absorbed into the
/// destination revisions, and if the source revision has no description.
///
/// The modification made by `jj absorb` can be reviewed by `jj op show -p`.
#[derive(clap::Args, Clone, Debug)]
pub(crate) struct AbsorbArgs {
    /// Source revision to absorb from
    #[arg(long, short, default_value = "@", value_name = "REVSET")]
    #[arg(add = ArgValueCompleter::new(complete::revset_expression_mutable))]
    from: RevisionArg,

    /// Destination revisions to absorb into
    ///
    /// Only ancestors of the source revision will be considered.
    #[arg(
        long,
        short = 't',
        visible_alias = "to",
        default_value = "mutable()",
        value_name = "REVSETS"
    )]
    #[arg(add = ArgValueCompleter::new(complete::revset_expression_mutable))]
    into: Vec<RevisionArg>,

    /// Move only changes to these paths (instead of all paths)
    #[arg(value_name = "FILESETS", value_hint = clap::ValueHint::AnyPath)]
    #[arg(add = ArgValueCompleter::new(complete::modified_from_files))]
    paths: Vec<String>,
}

#[instrument(skip_all)]
pub(crate) async fn cmd_absorb(
    ui: &mut Ui,
    command: &CommandHelper,
    args: &AbsorbArgs,
) -> Result<(), CommandError> {
    let mut workspace_command = command.workspace_helper(ui)?;

    let source_commit = workspace_command.resolve_single_rev(ui, &args.from).await?;
    let destinations = workspace_command
        .parse_union_revsets(ui, &args.into)?
        .resolve()?;

    let fileset_expression = workspace_command.parse_file_patterns(ui, &args.paths)?;
    let matcher = fileset_expression.to_matcher();

    let repo = workspace_command.repo().as_ref();
    let source = AbsorbSource::from_commit(repo, source_commit.clone()).await?;
    let selected_trees = split_hunks_to_trees(repo, &source, &destinations, &matcher).await?;

    print_unmatched_explicit_paths(
        ui,
        &workspace_command,
        &fileset_expression,
        [&source_commit.tree()],
    )?;

    let path_converter = workspace_command.path_converter();
    for (path, reason) in selected_trees.skipped_paths {
        let ui_path = path_converter.format_file_path(&path);
        writeln!(ui.warning_default(), "Skipping {ui_path}: {reason}")?;
    }

    workspace_command
        .check_rewritable(selected_trees.target_commits.keys())
        .await?;

    let mut tx = workspace_command.start_transaction();
    let stats = absorb_hunks(tx.repo_mut(), &source, selected_trees.target_commits).await?;

    if let Some(mut formatter) = ui.status_formatter() {
        if !stats.rewritten_destinations.is_empty() {
            writeln!(
                formatter,
                "Absorbed changes into {} revisions:",
                stats.rewritten_destinations.len()
            )?;
            print_updated_commits(
                formatter.as_mut(),
                &tx.commit_summary_template(),
                stats.rewritten_destinations.iter().rev(),
            )?;
        }
        if stats.num_rebased > 0 {
            writeln!(
                formatter,
                "Rebased {} descendant commits.",
                stats.num_rebased
            )?;
        }
    }

    tx.finish(
        ui,
        format!(
            "absorb changes into {} commits",
            stats.rewritten_destinations.len()
        ),
    )
    .await?;

    if let Some(mut formatter) = ui.status_formatter()
        && let Some(commit) = &stats.rewritten_source
    {
        let repo = workspace_command.repo().as_ref();
        if !commit.is_empty(repo).await? {
            writeln!(formatter, "Remaining changes:")?;
            let diff_renderer = workspace_command.diff_renderer(vec![DiffFormat::Summary]);
            let matcher = &EverythingMatcher; // also print excluded paths
            let width = ui.term_width();
            diff_renderer
                .show_patch(ui, formatter.as_mut(), commit, matcher, width)
                .await?;
        }
    }
    Ok(())
}
