//! Copyright (c) 2022-2026 GitDataAi All rights reserved.

use crate::bare::GitBare;
use crate::commit::create_commit::command_ok;
use crate::error::{GitError, GitResult};
use crate::pb::{CreateCommitResponse, GetCommitRequest, RevertCommitRequest};

const MAX_REVERT_PATCH_BYTES: usize = 100 * 1024 * 1024;

impl GitBare {
    pub fn revert_commit(&self, request: RevertCommitRequest) -> GitResult<CreateCommitResponse> {
        let target_branch = request.branch.clone();
        crate::sanitize::validate_ref_name(&target_branch)?;
        let revert_revision = match request.commit.and_then(|s| s.selector) {
            Some(crate::pb::object_selector::Selector::Oid(oid)) => {
                crate::sanitize::validate_oid_hex(&oid.hex)?;
                oid.hex
            }
            Some(crate::pb::object_selector::Selector::Revision(name)) => {
                crate::sanitize::validate_revision(&name.revision)?;
                name.revision
            }
            None => return Err(GitError::InvalidArgument("commit is required".into())),
        };

        let repo = self.gix_repo()?;

        let branch_ref = format!("refs/heads/{}", target_branch);
        let branch_tip = repo
            .find_reference(branch_ref.as_str())
            .ok()
            .and_then(|mut r| r.peel_to_id().ok())
            .map(|id| id.to_string())
            .ok_or_else(|| GitError::RefNotFound(target_branch.clone()))?;

        let revert_id = repo.rev_parse_single(revert_revision.as_str())?;
        let revert_obj = revert_id
            .object()?
            .try_into_commit()
            .map_err(|e| GitError::Gix(e.to_string()))?;

        let parent_ids: Vec<String> = revert_obj.parent_ids().map(|p| p.to_string()).collect();
        if parent_ids.len() > 1 {
            return Err(GitError::InvalidArgument(
                "reverting merge commits is not supported without mainline".into(),
            ));
        }
        let parent_hex = parent_ids
            .first()
            .ok_or_else(|| GitError::InvalidArgument("cannot revert root commit".into()))?;

        let tmp_index = tempfile::Builder::new()
            .prefix("gitks-revert-")
            .tempfile_in(&self.bare_dir)?;
        let idx_path = tmp_index.path().to_string_lossy().into_owned();
        let bare = self.bare_dir.to_string_lossy().into_owned();

        let read_tree = duct::cmd(
            "git",
            ["--git-dir", bare.as_str(), "read-tree", branch_tip.as_str()],
        )
        .env("GIT_INDEX_FILE", &idx_path)
        .stdout_capture()
        .stderr_capture()
        .unchecked()
        .run()?;
        command_ok(read_tree)?;

        let diff = duct::cmd(
            "git",
            [
                "--git-dir",
                bare.as_str(),
                "diff",
                "--binary",
                "--full-index",
                revert_revision.as_str(),
                parent_hex.as_str(),
            ],
        )
        .stdout_capture()
        .stderr_capture()
        .unchecked()
        .run()?;
        let patch_data = command_ok(diff)?;
        if patch_data.len() > MAX_REVERT_PATCH_BYTES {
            return Err(GitError::InvalidArgument(format!(
                "revert patch too large ({} bytes, max {MAX_REVERT_PATCH_BYTES})",
                patch_data.len()
            )));
        }

        let apply = duct::cmd(
            "git",
            [
                "--git-dir",
                bare.as_str(),
                "apply",
                "--cached",
                "--allow-empty",
                "-",
            ],
        )
        .env("GIT_INDEX_FILE", &idx_path)
        .stdin_bytes(patch_data.as_bytes())
        .stdout_capture()
        .stderr_capture()
        .unchecked()
        .run()?;
        if !apply.status.success() {
            return Err(GitError::Internal(format!(
                "revert apply failed: {}",
                String::from_utf8_lossy(&apply.stderr)
            )));
        }

        let write_tree = duct::cmd("git", ["--git-dir", bare.as_str(), "write-tree"])
            .env("GIT_INDEX_FILE", &idx_path)
            .stdout_capture()
            .stderr_capture()
            .unchecked()
            .run()?;
        let tree_id = command_ok(write_tree)?.trim().to_string();

        let subject = revert_obj
            .message_raw()?
            .to_string()
            .lines()
            .next()
            .unwrap_or_default()
            .to_string();
        let message = format!(
            "Revert \"{}\"\n\nThis reverts commit {}.",
            subject, revert_revision
        );

        let commit_id = self.commit_tree(
            &tree_id,
            std::slice::from_ref(&branch_tip),
            &message,
            request.committer.as_ref(),
            request.committer.as_ref(),
        )?;

        self.update_branch_ref(&target_branch, &commit_id, Some(&branch_tip), false)?;

        Ok(CreateCommitResponse {
            commit: Some(self.get_commit(GetCommitRequest {
                repository: request.repository,
                revision: Some(crate::pb::ObjectSelector {
                    selector: Some(crate::pb::object_selector::Selector::Revision(
                        crate::pb::ObjectName {
                            revision: commit_id,
                        },
                    )),
                }),
                include_stats: false,
                include_raw: false,
            })?),
            branch: target_branch,
        })
    }
}