to support type1 fonts, one needs a PostScript interpreter, as described here:

• https://adobe-type-tools.github.io/font-tech-notes/pdfs/T1_SPEC.pdf

there will be probably some need for a proper reference/specs: "PostScript Language Reference Manual"

• https://www.adobe.com/content/dam/acom/en/devnet/actionscript/articles/PLRM.pdf
• https://www.adobe.com/content/dam/acom/en/devnet/actionscript/articles/psrefman.pdf

a C-based, BSD, PostScript interpreter:

• https://github.com/luser-dr00g/xpost/tree/master/src/lib

Go-based interpreters/scanners/parsers:

• https://github.com/llgcode/ps
• https://github.com/moolekkari/unipdf/tree/master/ps
• https://github.com/creachadair/postscript
• https://github.com/golang/image/blob/master/font/sfnt/postscript.go