use crate::bare::GitBare;
use crate::error::{GitError, GitResult};
use crate::pb::{MergeRequest, MergeResult, merge_result};

impl GitBare {
    pub fn merge(&self, request: MergeRequest) -> GitResult<MergeResult> {
        let target_branch = request.target_branch.clone();
        crate::sanitize::validate_ref_name(&target_branch)?;
        let source_revision = match request.source.and_then(|s| s.selector) {
            Some(crate::pb::object_selector::Selector::Oid(oid)) => oid.hex.clone(),
            Some(crate::pb::object_selector::Selector::Revision(name)) => {
                crate::sanitize::validate_revision(&name.revision)?;
                name.revision.clone()
            }
            None => return Err(GitError::InvalidArgument("source is required".into())),
        };
        tracing::info!(
            repo = %self.bare_dir.display(),
            target = %target_branch,
            source = %source_revision,
            "merging"
        );
        let repo = self.gix_repo()?;

        let branch_ref = format!("refs/heads/{}", target_branch);
        let target_id = 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 source_id = repo.rev_parse_single(source_revision.as_str())?.to_string();

        if target_id == source_id {
            return Ok(MergeResult {
                status: merge_result::Status::MergeResultStatusAlreadyUpToDate as i32,
                commit: None,
                merge_base: Some(self.oid_to_pb(target_id)),
                conflicts: vec![],
                stats: None,
                message: String::from("Already up to date"),
            });
        }

        let target_oid = gix::hash::ObjectId::from_hex(target_id.as_bytes())
            .map_err(|e| GitError::InvalidOid(e.to_string()))?;
        let source_oid = gix::hash::ObjectId::from_hex(source_id.as_bytes())
            .map_err(|e| GitError::InvalidOid(e.to_string()))?;

        let merge_base = repo
            .merge_base(target_oid, source_oid)
            .ok()
            .map(|id| id.to_string());

        let ff_mode = request
            .options
            .as_ref()
            .map(|o| o.fast_forward)
            .unwrap_or(0);
        let ff_only =
            ff_mode == crate::pb::merge_options::FastForwardMode::MergeFastForwardModeOnly as i32;

        if let Some(ref base) = merge_base {
            if *base == target_id {
                let no_ff = ff_mode
                    == crate::pb::merge_options::FastForwardMode::MergeFastForwardModeNoFf as i32;

                if !no_ff {
                    self.update_branch_ref(&target_branch, &source_id, Some(&target_id), false)?;
                    return Ok(MergeResult {
                        status: merge_result::Status::MergeResultStatusFastForward as i32,
                        commit: None,
                        merge_base: Some(self.oid_to_pb(base.clone())),
                        conflicts: vec![],
                        stats: None,
                        message: format!("Fast-forward to {}", source_id),
                    });
                }
            }
            if *base == source_id {
                return Ok(MergeResult {
                    status: merge_result::Status::MergeResultStatusAlreadyUpToDate as i32,
                    commit: None,
                    merge_base: Some(self.oid_to_pb(base.clone())),
                    conflicts: vec![],
                    stats: None,
                    message: String::from("Already up to date"),
                });
            }
        }

        if ff_only {
            return Ok(MergeResult {
                status: merge_result::Status::MergeResultStatusAborted as i32,
                commit: None,
                merge_base: merge_base.map(|b| self.oid_to_pb(b)),
                conflicts: vec![],
                stats: None,
                message: String::from("Not possible to fast-forward"),
            });
        }

        let bare = self.bare_dir.to_string_lossy().into_owned();
        let result = duct::cmd(
            "git",
            [
                "--git-dir",
                bare.as_str(),
                "merge-tree",
                "--write-tree",
                "--no-messages",
                "-z",
                target_id.as_str(),
                source_id.as_str(),
            ],
        )
        .stdout_capture()
        .stderr_capture()
        .unchecked()
        .run()?;

        let stdout = String::from_utf8_lossy(&result.stdout).into_owned();

        if result.status.success() {
            let merged_tree = stdout.trim().to_string();
            let message = if !request.message.is_empty() {
                request.message.clone()
            } else {
                format!("Merge '{}' into {}", source_revision, target_branch)
            };

            let parents = vec![target_id.clone(), source_id.clone()];
            let commit_id = self.commit_tree(
                &merged_tree,
                &parents,
                &message,
                request.committer.as_ref(),
                request.committer.as_ref(),
            )?;

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

            Ok(MergeResult {
                status: merge_result::Status::MergeResultStatusMerged as i32,
                commit: Some(self.get_commit(crate::pb::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,
                })?),
                merge_base: merge_base.map(|b| self.oid_to_pb(b)),
                conflicts: vec![],
                stats: None,
                message,
            })
        } else {
            let conflicts = stdout
                .split('\0')
                .filter(|s| !s.is_empty())
                .map(|path| crate::pb::MergeConflict {
                    path: path.to_string(),
                    ..Default::default()
                })
                .collect();
            Ok(MergeResult {
                status: merge_result::Status::MergeResultStatusConflicts as i32,
                commit: None,
                merge_base: merge_base.map(|b| self.oid_to_pb(b)),
                conflicts,
                stats: None,
                message: String::from("Merge conflicts detected"),
            })
        }
    }
}