kerf-engine/engine/api/routes.py

"""API routes for the Kerf Engine trace and simplify endpoints."""

import json
import time

from fastapi import APIRouter, File, Form, HTTPException, UploadFile
from fastapi.responses import Response

from output import generate_dxf, generate_json, generate_svg
from pipeline.postprocess import postprocess_svg
from pipeline.preprocessing import preprocess
from pipeline.vectorize import potrace_trace, vtracer_trace

router = APIRouter()

VALID_MODES = {"potrace", "vtracer"}
VALID_OUTPUT_FORMATS = {"svg", "dxf", "json"}


def _format_response(
    result,
    output_format: str,
    warnings: list[str],
    processing_ms: float,
):
    """Build a standardized response from a PostProcessResult and output format.

    SVG and JSON return a JSON envelope with output + metadata.
    DXF returns raw bytes with application/dxf content type.
    """
    metadata = {
        "format": output_format,
        "path_count": len(result.paths),
        "node_count_total": result.total_nodes,
        "open_paths": result.open_path_count,
        "island_count": result.island_count,
        "warnings": warnings,
        "processing_ms": processing_ms,
    }

    if output_format == "dxf":
        dxf_bytes = generate_dxf(result)
        return Response(
            content=dxf_bytes,
            media_type="application/dxf",
            headers={
                "Content-Disposition": "attachment; filename=output.dxf",
                "X-Kerf-Metadata": json.dumps(metadata),
            },
        )
    elif output_format == "json":
        return {
            "output": json.loads(generate_json(result)),
            "format": "json",
            "metadata": metadata,
        }
    else:
        return {
            "output": generate_svg(result),
            "format": "svg",
            "metadata": metadata,
        }


@router.post("/engine/trace")
async def trace(
    file: UploadFile = File(...),
    mode: str = Form("potrace"),
    output_format: str = Form("svg"),
    preset: str = Form("default"),
    params: str = Form("{}"),
):
    """Convert a raster image to vector via the preprocessing + vectorization + post-processing pipeline.

    Supports three output formats: svg (default), dxf, json.
    """
    if mode not in VALID_MODES:
        raise HTTPException(
            status_code=422,
            detail=f"Invalid mode '{mode}'. Must be one of: {', '.join(sorted(VALID_MODES))}",
        )

    if output_format not in VALID_OUTPUT_FORMATS:
        raise HTTPException(
            status_code=422,
            detail=f"Unsupported output_format '{output_format}'. Must be one of: {', '.join(sorted(VALID_OUTPUT_FORMATS))}",
        )

    try:
        user_params = json.loads(params)
    except json.JSONDecodeError as exc:
        raise HTTPException(status_code=422, detail=f"Invalid params JSON: {exc}")

    raw_bytes = await file.read()
    if not raw_bytes:
        raise HTTPException(status_code=422, detail="Uploaded file is empty")

    warnings: list[str] = []
    start = time.perf_counter()

    try:
        preprocessed = preprocess(raw_bytes, params=user_params)
    except ValueError as exc:
        raise HTTPException(status_code=422, detail=f"Preprocessing failed: {exc}")

    try:
        if mode == "potrace":
            svg_output = potrace_trace(preprocessed, **{
                k: v for k, v in user_params.items()
                if k in ("turdsize", "alphamax", "opticurve", "opttolerance")
            })
        else:
            svg_output = vtracer_trace(preprocessed, **{
                k: v for k, v in user_params.items()
                if k in (
                    "colormode", "hierarchical", "filter_speckle", "color_precision",
                    "layer_difference", "corner_threshold", "length_threshold",
                    "splice_threshold", "mode", "path_precision", "max_iterations",
                )
            })
    except Exception as exc:
        raise HTTPException(status_code=500, detail=f"Vectorization failed: {exc}")

    # Post-processing: RDP simplification, island detection, open path analysis
    epsilon = float(user_params.get("epsilon", 1.0))
    try:
        result = postprocess_svg(svg_output, epsilon=epsilon)
    except Exception as exc:
        raise HTTPException(status_code=500, detail=f"Post-processing failed: {exc}")

    processing_ms = round((time.perf_counter() - start) * 1000, 2)

    return _format_response(result, output_format, warnings, processing_ms)


@router.post("/engine/simplify")
async def simplify(
    file: UploadFile = File(...),
    epsilon: float = Form(1.0),
    output_format: str = Form("svg"),
):
    """Simplify an existing SVG using RDP path simplification.

    Accepts an SVG file upload, applies Ramer-Douglas-Peucker simplification
    with the given epsilon, and returns the result in the requested format.
    """
    if output_format not in VALID_OUTPUT_FORMATS:
        raise HTTPException(
            status_code=422,
            detail=f"Unsupported output_format '{output_format}'. Must be one of: {', '.join(sorted(VALID_OUTPUT_FORMATS))}",
        )

    raw_bytes = await file.read()
    if not raw_bytes:
        raise HTTPException(status_code=422, detail="Uploaded file is empty")

    try:
        svg_str = raw_bytes.decode("utf-8")
    except UnicodeDecodeError:
        raise HTTPException(status_code=422, detail="File is not valid UTF-8 text")

    if "<svg" not in svg_str.lower():
        raise HTTPException(status_code=422, detail="File does not appear to be a valid SVG")

    warnings: list[str] = []
    start = time.perf_counter()

    try:
        result = postprocess_svg(svg_str, epsilon=epsilon)
    except Exception as exc:
        raise HTTPException(status_code=500, detail=f"Simplification failed: {exc}")

    processing_ms = round((time.perf_counter() - start) * 1000, 2)

    return _format_response(result, output_format, warnings, processing_ms)