move commit: Factor out the disconnection params

We can reuse the logic behind caculating the disconnect params.

Author: estib-vega

crates/but-workspace/src/branch/move_branch.rs

@@ -1,10 +1,5 @@
-use anyhow::{Context, bail};
 use but_core::RefMetadata;
-use but_graph::workspace::{Stack, StackSegment};
-use but_rebase::graph_rebase::{
-    Editor, Selector, SuccessfulRebase,
-    mutate::{SegmentDelimiter, SelectorSet, SomeSelectors},
-};
+use but_rebase::graph_rebase::SuccessfulRebase;
 
 /// Outcome of moving branches between or out of stacks.
 ///
@@ -20,12 +15,11 @@ pub struct Outcome<'ws, 'meta, M: RefMetadata> {
 
 pub(super) mod function {
 
+    use crate::branch::segment_disconnect::{DisconnectParameters, get_disconnect_parameters};
     use but_core::RefMetadata;
     use but_core::ref_metadata::StackId;
     use but_rebase::graph_rebase::mutate::SomeSelectors;
 
-    use super::get_disconnect_parameters;
-
     use super::Outcome;
     use anyhow::Context;
     use anyhow::bail;
@@ -105,14 +99,17 @@ pub(super) mod function {
             .select_reference(lower_bound_ref)
             .context("Failed to find target reference in graph.")?;
 
-        let (subject_delimiter, children_to_disconnect, parents_to_disconnect) =
-            get_disconnect_parameters(
-                &editor,
-                &workspace,
-                source_stack,
-                subject_segment,
-                workspace_head,
-            )?;
+        let DisconnectParameters {
+            delimiter: subject_delimiter,
+            children_to_disconnect,
+            parents_to_disconnect,
+        } = get_disconnect_parameters(
+            &editor,
+            &workspace,
+            source_stack,
+            subject_segment,
+            workspace_head,
+        )?;
 
         editor.disconnect_segment_from(
             subject_delimiter.clone(),
@@ -202,14 +199,17 @@ pub(super) mod function {
             .select_reference(target_segment_ref_name)
             .context("Failed to find target reference in graph.")?;
 
-        let (subject_delimiter, children_to_disconnect, parents_to_disconnect) =
-            get_disconnect_parameters(
-                &editor,
-                &workspace,
-                &source_stack,
-                &subject_segment,
-                workspace_head,
-            )?;
+        let DisconnectParameters {
+            delimiter: subject_delimiter,
+            children_to_disconnect,
+            parents_to_disconnect,
+        } = get_disconnect_parameters(
+            &editor,
+            &workspace,
+            &source_stack,
+            &subject_segment,
+            workspace_head,
+        )?;
 
         let skip_reconnect_step = source_stack.segments.len() == 1;
         editor.disconnect_segment_from(
@@ -311,158 +311,3 @@ pub(super) mod function {
         Ok((own_context(source), own_context(destination)))
     }
 }
-
-/// Get the right disconnect parameters for the given subject segment and source stack.
-///
-/// This function determines which are the right parents and children to disconnect,
-/// as well as the right segment delimiter to move.
-fn get_disconnect_parameters<'ws, 'meta, M: RefMetadata>(
-    editor: &Editor<'ws, 'meta, M>,
-    workspace: &but_graph::Workspace,
-    source_stack: &Stack,
-    subject_segment: &StackSegment,
-    workspace_head: gix::ObjectId,
-) -> anyhow::Result<(
-    SegmentDelimiter<Selector, Selector>,
-    SelectorSet,
-    SelectorSet,
-)> {
-    let index_of_segment = source_stack
-        .segments
-        .iter()
-        .position(|segment| segment.id == subject_segment.id)
-        .context("BUG: Unable to find subject segment on source stack.")?;
-
-    let subject_segment_ref_name = subject_segment
-        .ref_name()
-        .context("Subject segment doesn't have a ref name.")?;
-    let delimiter_child = editor
-        .select_reference(subject_segment_ref_name)
-        .context("Failed to find subject reference in graph.")?;
-    let delimiter_parent = match subject_segment.commits.last() {
-        Some(last_commit) => editor
-            .select_commit(last_commit.id)
-            .context("Failed to find last commit in subject segment in graph.")?,
-        None => {
-            // Subject segment is empty, move only the reference
-            delimiter_child
-        }
-    };
-
-    // The delimiter for the segment we want to move, is the reference selector
-    // as the child, and the last commit inside the branch as the parent.
-    // If the branch is empty, we take the reference selector as the parent as well.
-    let delimiter = SegmentDelimiter {
-        child: delimiter_child,
-        parent: delimiter_parent,
-    };
-
-    // The parent segment in the stack if any.
-    // This will be `None` if the branch we want to move is at the bottom of the stack.
-    let stack_base_segment = subject_segment.base_segment_id.and_then(|base_segment_id| {
-        source_stack
-            .segments
-            .iter()
-            .find(|segment| segment.id == base_segment_id)
-    });
-
-    // The parent segment in the graph.
-    // If the `stack_base_segment` is `None` but there's a `base_segment_id` defined, it means we'll find it in the
-    // graph data, and it's probably the target branch, which is not included in the workspace.
-    let graph_base_segment = subject_segment
-        .base_segment_id
-        .map(|segment_idx| &workspace.graph[segment_idx]);
-
-    let parents_to_disconnect = if let Some(stack_base_segment) = stack_base_segment {
-        // Base segment is part of the source stack.
-        select_segment(editor, stack_base_segment)?
-    } else if let Some(graph_base_segment) = graph_base_segment {
-        // Base segment is outside of workspace (probably target branch).
-        select_segment(editor, graph_base_segment)?
-    } else if subject_segment.base_segment_id.is_some() {
-        // Base segment could not be found, but there is an ID defined. Error out.
-        bail!(
-            "Failed to find the base segment of the subject we want to move, even if it seems to be defined"
-        );
-    } else {
-        // Nothing found. Remove all parents.
-        SelectorSet::All
-    };
-
-    if index_of_segment == 0 {
-        // This is the top-most segment in the stack, so the parent is the workspace commit.
-        let workspace_head_selector = editor
-            .select_commit(workspace_head)
-            .context("Failed to find workspace head in graph.")?;
-        let selectors = SomeSelectors::new(vec![workspace_head_selector])?;
-        let children_to_disconnect = SelectorSet::Some(selectors);
-
-        return Ok((delimiter, children_to_disconnect, parents_to_disconnect));
-    }
-
-    // Segment on top of the subject segment in the stack.
-    let child_segment = source_stack.segments.get(index_of_segment - 1).context(
-        "BUG: Unable to find child segment of subject segment but expected it to exist.",
-    )?;
-
-    // If branch stacked on top of the branch we want to move is empty, we only need to disconnect
-    // the reference from it.
-    // Otherwise, disconnect the last commit on the segment.
-    let child_selector = match child_segment.commits.last() {
-        Some(last_commit) => editor
-            .select_commit(last_commit.id)
-            .context("Failed to find last commit of child segment in graph."),
-        None => {
-            // The segment on top of the subject segment is empty. Select the reference.
-            let child_segment_ref_name = child_segment
-                .ref_name()
-                .context("Child segment doesn't have a ref name.")?;
-            editor
-                .select_reference(child_segment_ref_name)
-                .context("Failed to find child segment reference in graph.")
-        }
-    }?;
-    let selectors = SomeSelectors::new(vec![child_selector])?;
-    let children_to_disconnect = SelectorSet::Some(selectors);
-
-    Ok((delimiter, children_to_disconnect, parents_to_disconnect))
-}
-
-/// Select a segment by its ref name if available, otherwise fall back to its tip commit.
-fn select_segment<M: RefMetadata>(
-    editor: &Editor<'_, '_, M>,
-    segment: &impl SegmentLike,
-) -> anyhow::Result<SelectorSet> {
-    let selector = if let Some(ref_name) = segment.ref_name() {
-        editor.select_reference(ref_name)?
-    } else if let Some(tip) = segment.tip() {
-        editor.select_commit(tip)?
-    } else {
-        bail!("Base segment has neither a ref name nor any commits.");
-    };
-    let selectors = SomeSelectors::new(vec![selector])?;
-    Ok(SelectorSet::Some(selectors))
-}
-
-trait SegmentLike {
-    fn ref_name(&self) -> Option<&gix::refs::FullNameRef>;
-    fn tip(&self) -> Option<gix::ObjectId>;
-}
-
-impl SegmentLike for StackSegment {
-    fn ref_name(&self) -> Option<&gix::refs::FullNameRef> {
-        self.ref_name()
-    }
-    fn tip(&self) -> Option<gix::ObjectId> {
-        self.tip()
-    }
-}
-
-impl SegmentLike for but_graph::Segment {
-    fn ref_name(&self) -> Option<&gix::refs::FullNameRef> {
-        self.ref_name()
-    }
-    fn tip(&self) -> Option<gix::ObjectId> {
-        self.tip()
-    }
-}