use crate::bare::GitBare;
use crate::error::{GitError, GitResult};
use crate::pb::{GetCommitDiffRequest, GetDiffRequest, GetDiffResponse};

impl GitBare {
    pub fn get_commit_diff(&self, request: GetCommitDiffRequest) -> GitResult<GetDiffResponse> {
        let commit = match request.commit.and_then(|s| s.selector) {
            Some(crate::pb::object_selector::Selector::Oid(oid)) => oid.hex,
            Some(crate::pb::object_selector::Selector::Revision(name)) => name.revision,
            None => "HEAD".into(),
        };
        let base = self.first_parent_or_empty_tree(&commit)?;
        self.get_diff(GetDiffRequest {
            repository: request.repository,
            base: Some(crate::pb::ObjectSelector {
                selector: Some(crate::pb::object_selector::Selector::Revision(
                    crate::pb::ObjectName { revision: base },
                )),
            }),
            head: Some(crate::pb::ObjectSelector {
                selector: Some(crate::pb::object_selector::Selector::Revision(
                    crate::pb::ObjectName { revision: commit },
                )),
            }),
            options: request.options,
            pagination: request.pagination,
        })
    }

    fn first_parent_or_empty_tree(&self, commit: &str) -> GitResult<String> {
        let result = duct::cmd(
            "git",
            [
                "--git-dir",
                self.bare_dir.to_string_lossy().as_ref(),
                "rev-list",
                "--parents",
                "-n",
                "1",
                commit,
            ],
        )
        .stdout_capture()
        .stderr_capture()
        .unchecked()
        .run()?;
        if !result.status.success() {
            return Err(GitError::CommandFailed {
                status_code: result.status.code(),
                stderr: String::from_utf8_lossy(&result.stderr).into_owned(),
            });
        }
        let output = String::from_utf8_lossy(&result.stdout);
        let parts = output.split_whitespace().collect::<Vec<_>>();
        if let Some(parent) = parts.get(1) {
            return Ok((*parent).to_string());
        }

        let empty_tree = duct::cmd(
            "git",
            [
                "--git-dir",
                self.bare_dir.to_string_lossy().as_ref(),
                "hash-object",
                "-t",
                "tree",
                "-w",
                "--stdin",
            ],
        )
        .stdin_bytes(Vec::<u8>::new())
        .stdout_capture()
        .stderr_capture()
        .unchecked()
        .run()?;
        if !empty_tree.status.success() {
            return Err(GitError::CommandFailed {
                status_code: empty_tree.status.code(),
                stderr: String::from_utf8_lossy(&empty_tree.stderr).into_owned(),
            });
        }
        Ok(String::from_utf8_lossy(&empty_tree.stdout)
            .trim()
            .to_string())
    }
}