Implement FlowchartGenerator for Python-to-flowchart conversion

[Copilot]

Implements the missing FlowchartGenerator class to convert Python code from the code editor into flowchart blocks and connections for the visualization panel, following placement rules in FlowSight_Rules.md.

Implementation

• src/flowsight/engine/flowchart.py (342 lines)
  • Parses Python code, filters executable lines (strips comments, imports, blank lines)
  • Places blocks in depth-first, lexical order per specification
  • Generates connections with proper port assignments (N/S/E/W)
  • Converts grid coordinates to pixel coordinates with configurable layout parameters

Placement Algorithm

Strict rule compliance:

• Each executable line → exactly one block
• Start at grid (0,0), first code at (1,0), End positioned below all code
• Sequential blocks: +1 row, same column
• If/elif/else chains: True body directly below, False branches +1 column right
• For/while loops: body at (+1 row, +1 col), back edge from last body to header south port

Port usage matches specification:

• Process blocks: N (in), S (out), W (back-out)
• If/elif headers: N (in), S (True), E (False)
• Loop headers: N (in), E (True), S (back-in), W (False/exit)

Example Usage

gen = FlowchartGenerator(margin_left=50, margin_top=50, col_width=150, row_height=80)
blocks, connections = gen.generate(code)
# Returns block dicts with {line_num, text, type, row, col, x, y, width, height}
# and connection dicts with {from, to, from_port, to_port, label}

Testing & Documentation

• test_flowchart.py: 8 test cases covering sequential, conditionals, loops, nested structures, edge cases
• docs/FlowchartGenerator_Implementation.md: Technical details, algorithms, data structures
• docs/FlowchartGenerator_QuickStart.md: Usage reference and examples

All example files (fibonacci, conditionals, loops) generate correct flowcharts. Integration with ExecutionEngine already in place via existing import.

Original prompt

Using the FlowSight_Rules.md and associated files in the Rules for Reference folder, create the FlowchartGenerator and associated scripts that the software needs to convert the code from the code_editor to the visualization panel.

Take extra note of these absolute rules:

• Each line of code is always converted to exactly one block on the diagram (omitting comments, blank lines, and imports and stripping in-line comments)
• Blocks are placed one at a time in the order they appear in the code editor
• Block placement is completely determined by direct target. A block may place only blocks it is directly connected to.
• Because blocks are placed in the order they appear in the code editor, naturally, a header block will first place its child, wait until that child has placed its child, and so on, before then finally afterwards, placing its sequential successor

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