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# Flowchart Parser
As mentioned in the previous section, we use [getDiagramFromText](https://github.com/mermaid-js/mermaid/blob/00d06c7282a701849793680c1e97da1cfdfcce62/packages/mermaid/src/Diagram.ts#L80) to parse the full defination and get the [Diagram](https://github.com/mermaid-js/mermaid/blob/00d06c7282a701849793680c1e97da1cfdfcce62/packages/mermaid/src/Diagram.ts#L15) json from it.
In this section we will be diving into how the [flowchart parser](https://github.com/excalidraw/mermaid-to-excalidraw/blob/master/src/parser/flowchart.ts#L256) works behind the scenes.
We use `diagram.parser.yy` attribute to parse the data. If you want to know more about how the `diagram.parse.yy` attribute looks like, you can check it [here](https://github.com/mermaid-js/mermaid/blob/00d06c7282a701849793680c1e97da1cfdfcce62/packages/mermaid/src/diagrams/flowchart/flowDb.js#L768), however for scope of flowchart we are using **3** APIs from this parser to compute `vertices`, `edges` and `clusters` as we need these data to transform to [ExcalidrawElementSkeleton](https://github.com/excalidraw/excalidraw/blob/master/packages/excalidraw/data/transform.ts#L133C13-L133C38).
For computing `vertices` and `edge`s lets consider the below svg generated by mermaid
## Computing the vertices
We use `getVertices` API from `diagram.parse.yy` to get the vertices for a given flowchart.
Considering the same example this is the response from the API
```js
{
"start": {
"id": "start",
"labelType": "text",
"domId": "flowchart-start-1414",
"styles": [],
"classes": [],
"text": "start",
"props": {}
},
"stop": {
"id": "stop",
"labelType": "text",
"domId": "flowchart-stop-1415",
"styles": [],
"classes": [],
"text": "stop",
"props": {}
}
}
```
The dimensions and position is missing in this response and we need that to transform to [ExcalidrawElementSkeleton](https://github.com/excalidraw/excalidraw/blob/master/packages/excalidraw/data/transform.ts#L133C13-L133C38), for this we have our own parser [`parseVertex`](https://github.com/excalidraw/mermaid-to-excalidraw/blob/master/src/parseMermaid.ts#L178) which takes the above response and uses the `svg` together to compute position, dimensions and cleans up the response.
The final output from `parseVertex` looks like :point_down:
```js
{
"start": {
"id": "start",
"labelType": "text",
"text": "start",
"x": 0,
"y": 0,
"width": 67.796875,
"height": 44,
"containerStyle": {},
"labelStyle": {}
},
"stop": {
"id": "stop",
"labelType": "text",
"text": "stop",
"x": 117.796875,
"y": 0,
"width": 62.3828125,
"height": 44,
"containerStyle": {},
"labelStyle": {}
}
}
```
## Computing the edges
The lines and arrows are considered as `edges` in mermaid as shown in the above diagram.
We use `getEdges` API from `diagram.parse.yy` to get the edges for a given flowchart.
Considering the same example this is the response from the API
```js
[
{
"start": "start",
"end": "stop",
"type": "arrow_point",
"text": "",
"labelType": "text",
"stroke": "normal",
"length": 1
}
]
```
Similarly here the dimensions and position is missing and we compute that from the svg. The [`parseEdge`](https://github.com/excalidraw/mermaid-to-excalidraw/blob/master/src/parseMermaid.ts#L245) takes the above response along with `svg` and computes the position, dimensions and cleans up the response.
The final output from `parseEdge` looks like :point_down:
```js
[
{
"start": "start",
"end": "stop",
"type": "arrow_point",
"text": "",
"labelType": "text",
"stroke": "normal",
"startX": 67.797,
"startY": 22,
"endX": 117.797,
"endY": 22,
"reflectionPoints": [
{
"x": 67.797,
"y": 22
},
{
"x": 117.797,
"y": 22
}
]
}
]
```
## Computing the Subgraphs
`Subgraphs` is collection of elements grouped together. The Subgraphs map to `grouping` elements in Excalidraw.
Lets consider the below example :point_down:
We use `getSubgraphs` API to get the subgraph data for a given flowchart.
Considering the same example this is the response from the API
```js
[
{
"id": "one",
"nodes": [
"flowchart-a2-1399",
"flowchart-a1-1400"
],
"title": "one",
"classes": [],
"labelType": "text"
}
]
```
For position and dimensions we use the svg to compute. The [`parseSubgraph`](https://github.com/excalidraw/mermaid-to-excalidraw/blob/master/src/parseMermaid.ts#L139) takes the above response along with `svg` and computes the position, dimensions and cleans up the response.
```js
[
{
"id": "one",
"nodes": [
"flowchart-a2-1399",
"flowchart-a1-1400"
],
"title": "one",
"labelType": "text",
"nodeIds": [
"a2",
"a1"
],
"x": 75.4921875,
"y": 0,
"width": 121.25,
"height": 188,
"text": "one"
}
]
```
|
