lix 0.16.0

Embeddable version control for apps and AI agents.
Documentation 
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use crate::LixError;
use crate::branch::{
    BranchLifecycle, BranchOperation, BranchReferenceRole, branch_descriptor_stage_row,
    branch_ref_stage_row,
};
use crate::storage_adapter::Storage;
use crate::transaction_types::{RawWriteBatch, TransactionWrite, TransactionWriteMode};

use super::context::SessionContext;

/// Options for creating a new branch from the session's active branch.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct CreateBranchOptions {
    /// Optional caller-provided branch id. If omitted, engine generates one.
    pub id: Option<String>,
    /// User-facing branch name.
    pub name: String,
    /// Optional commit id for the new branch head. If omitted, the current
    /// active branch head is used.
    pub from_commit_id: Option<String>,
}

/// Receipt returned after creating a branch.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct CreateBranchReceipt {
    pub id: String,
    pub name: String,
    pub hidden: bool,
    pub commit_id: String,
}

impl<StorageImpl> SessionContext<StorageImpl>
where
    StorageImpl: Storage + Clone + Send + Sync + 'static,
{
    /// Creates a new branch from this session's current branch head.
    ///
    /// Branch descriptors are tracked global facts so every branch agrees on
    /// which branches exist. Branch refs are untracked global moving pointers:
    /// each update is a changelog fact, but never a commit member.
    pub async fn create_branch(
        &self,
        options: CreateBranchOptions,
    ) -> Result<CreateBranchReceipt, LixError> {
        self.with_write_transaction_lending(async move |transaction| {
            let CreateBranchOptions {
                id,
                name,
                from_commit_id,
            } = options;
            let branch_id =
                id.unwrap_or_else(|| transaction.functions().call_uuid_v7().to_string());
            let explicit_historical_source = from_commit_id.is_some();
            let source_head = if let Some(from_commit_id) = from_commit_id {
                let from_commit_id = BranchLifecycle::parse_commit_id(
                    &from_commit_id,
                    BranchOperation::CreateBranch,
                    BranchReferenceRole::CommitSource,
                )?;
                let mut commit_graph = transaction.commit_graph_reader().await?;
                let commit = BranchLifecycle::require_existing_commit(
                    &mut commit_graph,
                    from_commit_id,
                    BranchOperation::CreateBranch,
                    BranchReferenceRole::CommitSource,
                )
                .await?;
                commit.commit_id
            } else {
                let active_branch_id = transaction.active_branch_id().to_string();
                let reader = transaction.branch_ref_reader().await?;
                BranchLifecycle::new(&reader)
                    .require_existing_commit_id(
                        &active_branch_id,
                        BranchOperation::CreateBranch,
                        BranchReferenceRole::Source,
                    )
                    .await?
            };

            let mut rows = RawWriteBatch::with_capacity(2);
            rows.push(branch_descriptor_stage_row(&branch_id, &name, false));
            rows.push(branch_ref_stage_row(&branch_id, &source_head));
            transaction
                .stage_write(TransactionWrite::Rows {
                    mode: TransactionWriteMode::Insert,
                    rows,
                })
                .await?;
            if explicit_historical_source {
                transaction.stage_branch_checkpoint_replacement_resolution(
                    branch_id.clone(),
                    source_head,
                )?;
            }

            Ok(CreateBranchReceipt {
                id: branch_id,
                name,
                hidden: false,
                commit_id: source_head.to_string(),
            })
        })
        .await
    }
}