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digraph_prettyprinter.go
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digraph_prettyprinter.go
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// Copyright © 2016 Asteris, LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package prettyprinters
import "github.com/asteris-llc/converge/graph"
// Hey! Are you here to get output before any node but after all the nodes?
// Well, that doesn't exist right now. If you need it, you should add it.
// It used to be `StartNodeSection` and `FinishNodeSection`, so maybe call it
// `NodeSectionPrinter` and add those methods.
// BasePrinter is an implementation of some output format that can be used to
// prettyprint a Directed Graph. Printer is the zero value for these kinds of
// printers. To get any functionality, printers should implement one or more of
// the following interfaces.
type BasePrinter interface{}
// GraphPrinter should be implemented by printers that need to add a preamble or
// addendum to the pretty printed output
type GraphPrinter interface {
// StartPP should take a graph and shall return a string used to start the
// graph output, or an error which will be returned to the user.
StartPP(graph *graph.Graph) (Renderable, error)
// FinishPP will be given a graph and shall return a string used to finalize
// graph output, or an error which will be returned to the user.
FinishPP(graph *graph.Graph) (Renderable, error)
}
// SubgraphPrinter should be implemented by printers that need to control
// subgraph rendering (that is, grouping of nodes of any kind)
type SubgraphPrinter interface {
// MarkNode() is a function used to identify the boundaries of subgraphs
// within the larger graph. MarkNode() is called with a graph and the id of a
// node within the graph, and should return a *SubgraphMarker with the
// SubgraphID and Start fields set to indicate the beginning or end of a
// subgraph. If nil is returned the node will be included in the subgraph of
// it's parent (or ⊥ if it is not part of any subgraph).
// The string "⊥" is reserved for the bottom subgraph element and shouldn't be
// used as a NodeID.
MarkNode(graph *graph.Graph, nodeID string) *SubgraphMarker
// StartSubgraph will be given a graph, the ID of the root node of the
// subgraph, and the SubgraphID returned as part of MarkNode(). It should
// return the string used to start the subgraph or an error that will be
// returned to the user.
StartSubgraph(graph *graph.Graph, nodeID string, subgraphID SubgraphID) (Renderable, error)
// FinishSubgraph will be given a graph and a SubgraphID returned by MarkNode
// and should return a string used to end a subgraph, or an error that will be
// returned to the user.
FinishSubgraph(graph *graph.Graph, subgraphID SubgraphID) (Renderable, error)
}
// NodePrinter should be implemented by printers that want to render nodes
type NodePrinter interface {
// DrawNode will be called once for each node in the graph. The function will
// be given a graph and a string ID for the current node in the graph, and
// should return a string representing the node in the final output, or an
// error that will be returned to the user.
DrawNode(graph *graph.Graph, nodeID string) (Renderable, error)
}
// EdgeSectionPrinter should be implemented by printers that want to render edge sections (TODO: what are these?)
type EdgeSectionPrinter interface {
// StartEdgeSection will be given a graph and should return a string used to
// start the edge section, or an error that will be returned to the user.
StartEdgeSection(graph *graph.Graph) (Renderable, error)
// FinishEdgeSection will be given a graph and should return a string used to
// finish the edge section in the final output, or an error that will be
// returned to the user.
FinishEdgeSection(graph *graph.Graph) (Renderable, error)
}
// EdgePrinter should be implemented by printers that want to render Edges
type EdgePrinter interface {
// DrawEdge will be called once for each edge in the graph. It is called with
// a graph, the ID of the source vertex, and the ID of the target vertex. It
// should return a string representing the edge in the final output, or an
// error that will be returned to the user.
DrawEdge(graph *graph.Graph, srcNodeID string, dstNodeID string) (Renderable, error)
}