368 lines
14 KiB
Org Mode
368 lines
14 KiB
Org Mode
#+TITLE: ParenScript Conversion Experiment
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#+AUTHOR: Glenn
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#+DATE: 2025-11-06
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* Overview
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This branch experiments with converting all JavaScript files to ParenScript, allowing us to write client-side code in Common Lisp that compiles to JavaScript.
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* Goals
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- Replace all =.js= files with ParenScript equivalents
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- Maintain same functionality
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- Improve code maintainability by using one language (Lisp) for both frontend and backend
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- Take advantage of Lisp macros for client-side code generation
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* Current JavaScript Files
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- =static/js/admin.js= - Admin dashboard functionality
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- =static/js/auth-ui.js= - Authentication UI
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- =static/js/front-page.js= - Front page interactions
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- =static/js/player.js= - Audio player controls
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- =static/js/profile.js= - User profile page
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- =static/js/users.js= - User management
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* Implementation Plan
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** Phase 1: Setup [DONE]
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- [X] Add ParenScript dependency to =asteroid.asd=
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- [X] Create =parenscript-utils.lisp= with helper functions
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- [X] Create experimental branch
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** Phase 2: Convert Simple Files First
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- [X] Convert =auth-ui.js= (smallest, simplest) - COMPLETE ✅
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- [X] Convert =front-page.js= (stream quality, now playing, pop-out, frameset) - COMPLETE ✅
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- [X] Convert =profile.js= (user profile, stats, history) - COMPLETE ✅
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- [X] Convert =users.js= (user management, admin) - COMPLETE ✅
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** Phase 3: Convert Complex Files
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- [X] Convert =player.js= (audio player logic) - COMPLETE ✅
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- [X] Convert =admin.js= (queue management, track controls) - COMPLETE ✅
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** Phase 4: Testing & Refinement
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- [ ] Test all functionality
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- [ ] Optimize generated JavaScript
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- [ ] Document ParenScript patterns used
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* Benefits
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** Code Reuse
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- Share utility functions between frontend and backend
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- Use same data structures and validation logic
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** Macros
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- Create domain-specific macros for common UI patterns
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- Generate repetitive JavaScript code programmatically
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** Type Safety
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- Catch more errors at compile time
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- Better IDE support with Lisp tooling
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** Maintainability
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- Single language for entire stack
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- Easier refactoring across frontend/backend boundary
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* ParenScript Resources
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- [[https://parenscript.common-lisp.dev/][ParenScript Documentation]]
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- [[https://gitlab.common-lisp.net/parenscript/parenscript][ParenScript GitLab Repository]]
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- [[https://parenscript.common-lisp.dev/reference.html][ParenScript Reference Manual]]
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* Lessons Learned
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** auth-ui.js Conversion (2025-11-06)
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*** Challenge 1: Route Precedence
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*Problem:* Radiance routes are matched in load order, not definition order. The general static file route (=/static/(.*)=) was intercepting our specific ParenScript route.
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*Solution:* Intercept the static file route and check if path is =js/auth-ui.js=. If yes, serve ParenScript; otherwise serve regular file.
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*** Challenge 2: Async/Await Syntax
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*Problem:* ParenScript doesn't support =async/await= syntax. Using =(async lambda ...)= generated invalid JavaScript.
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*Solution:* Use promise chains with =.then()= instead of async/await.
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*** Challenge 3: Compile Time vs Runtime
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*Problem:* ParenScript compiler (=ps:ps*=) isn't available in saved binary at runtime.
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*Solution:* Compile JavaScript at load time and store in a parameter. The function just returns the pre-compiled string.
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*** Success Metrics
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- JavaScript compiles correctly (1386 characters)
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- No browser console errors
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- Auth UI works perfectly (show/hide elements based on login status)
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- Generated code is readable and maintainable
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*** Key Patterns
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*Compile at load time:*
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#+BEGIN_EXAMPLE
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(defparameter *my-js*
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(ps:ps* '(progn ...)))
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(defun generate-my-js ()
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*my-js*)
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#+END_EXAMPLE
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*Promise chains instead of async/await:*
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#+BEGIN_EXAMPLE
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(ps:chain (fetch url)
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(then (lambda (response) (ps:chain response (json))))
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(then (lambda (data) (process data)))
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(catch (lambda (error) (handle error))))
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#+END_EXAMPLE
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*Intercept static route:*
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#+BEGIN_EXAMPLE
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(define-page static #@"/static/(.*)" (:uri-groups (path))
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(if (string= path "js/my-file.js")
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(serve-parenscript)
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(serve-static-file)))
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#+END_EXAMPLE
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* Notes
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This is an EXPERIMENTAL branch. The goal is to evaluate ParenScript for this project, not to immediately replace all JavaScript.
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If successful, we can merge incrementally, one file at a time.
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** Conversion Progress
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- *auth-ui.js* (2025-11-06): Successfully converted. 1386 chars. All functionality working.
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- *front-page.js* (2025-11-06): Successfully converted. 6900 chars. Stream quality, now playing, pop-out player, frameset mode all working.
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- *profile.js* (2025-11-06): Successfully converted. Profile data, listening stats, recent tracks, top artists, password change all working.
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- *users.js* (2025-11-06): Successfully converted. User stats, user list, role changes, activate/deactivate, create user all working.
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** front-page.js Conversion Notes
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This was a more complex file with multiple features. Key learnings:
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*** Global Variables
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ParenScript uses =(defvar *variable-name* value)= for global variables:
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#+BEGIN_EXAMPLE
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(defvar *popout-window* nil)
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#+END_EXAMPLE
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*** String Concatenation
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Use =+= operator for string concatenation:
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#+BEGIN_EXAMPLE
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(+ "width=" width ",height=" height)
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#+END_EXAMPLE
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*** Conditional Logic
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Use =cond= for multiple conditions in route interception:
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#+BEGIN_EXAMPLE
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(cond
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((string= path "js/auth-ui.js") ...)
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((string= path "js/front-page.js") ...)
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(t ...))
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#+END_EXAMPLE
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*** Object Property Access
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Use =ps:getprop= for dynamic property access:
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#+BEGIN_EXAMPLE
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(ps:getprop config encoding) ; config[encoding]
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#+END_EXAMPLE
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All features tested and working:
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- Stream quality selector changes stream correctly
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- Now playing updates every 10 seconds
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- Pop-out player functionality works
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- Frameset mode toggle works
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- Auto-reconnect on stream errors works
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** profile.js and users.js Conversion Notes
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*** Modulo Operator
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ParenScript doesn't support =%= for modulo. Use =rem= (remainder) instead:
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#+BEGIN_EXAMPLE
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;; WRONG:
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(% seconds 3600)
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;; CORRECT:
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(rem seconds 3600)
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#+END_EXAMPLE
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*** Property Access with Hyphens
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For properties with hyphens (like ="last-login"=), use =ps:getprop=:
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#+BEGIN_EXAMPLE
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(ps:getprop user "last-login")
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;; Instead of (ps:@ user last-login)
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#+END_EXAMPLE
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*** Template Literals in HTML Generation
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Build HTML strings with =+= concatenation:
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#+BEGIN_EXAMPLE
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(+ "<td>" (ps:@ user username) "</td>"
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"<td>" (ps:@ user email) "</td>")
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#+END_EXAMPLE
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*** Conditional Attributes
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Use =if= expressions inline for conditional HTML attributes:
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#+BEGIN_EXAMPLE
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(+ "<option value=\"listener\" "
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(if (= (ps:@ user role) "listener") "selected" "")
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">Listener</option>")
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#+END_EXAMPLE
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** player.js Conversion Notes (2025-11-07)
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This was the most challenging conversion due to complex ParenScript compilation errors and server-side error handling issues.
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*** Challenge 1: PUSH Macro Conflict
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*Problem:* Using =(push item array)= in ParenScript context caused "Error while parsing arguments to DEFMACRO PUSH" because ParenScript doesn't have a PUSH macro like Common Lisp.
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*Solution:* Use array index assignment instead:
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#+BEGIN_EXAMPLE
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;; WRONG:
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(push item *play-queue*)
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;; CORRECT (what I implemented):
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(setf (aref *play-queue* (ps:@ *play-queue* length)) item)
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;; ALTERNATIVE (more idiomatic, could be used instead):
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(ps:chain *play-queue* (push item))
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;; This compiles to: playQueue.push(item);
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#+END_EXAMPLE
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*Note:* According to the ParenScript reference manual (=/home/glenn/Projects/Code/parenscript/docs/reference.html=, lines 672, 745-750), the =CHAIN= macro is designed to chain together accessors and function calls. This means =(ps:chain array (push item))= is actually valid ParenScript and would call the JavaScript =push= method. Our current implementation using =setf= and =aref= works correctly but is more verbose. The =chain= approach would be more idiomatic JavaScript.
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*** Challenge 2: != Operator
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*Problem:* ParenScript translates =!=== to a function called =bangequals= which doesn't exist, causing "bangequals is not defined" runtime error.
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*Solution:* Use =(not (== ...))= instead:
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#+BEGIN_EXAMPLE
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;; WRONG:
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(!= value expected)
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;; CORRECT:
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(not (== value expected))
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#+END_EXAMPLE
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*** Challenge 3: Error Variable Names in handler-case
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*Problem:* ANY variable name used in error handler clauses (=e=, =err=, =connection-err=, =condition-object=) was being interpreted as an undefined function call, causing errors like "The function ASTEROID::ERR is undefined" or "The function COMMON-LISP:CONDITION is undefined".
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*Root Cause:* When error variables were used in =format= statements within =handler-case= error handlers, something in the error handling chain was trying to evaluate them as function calls instead of variables.
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*Solution:* Remove error variable bindings entirely and don't try to print the error object:
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#+BEGIN_EXAMPLE
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;; WRONG:
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(handler-case
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(risky-operation)
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(error (err)
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(format t "Error: ~a~%" err) ; err gets evaluated as function!
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nil))
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;; CORRECT:
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(handler-case
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(risky-operation)
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(error ()
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(format t "Error occurred~%") ; No variable to evaluate
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nil))
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#+END_EXAMPLE
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*** Challenge 4: Parenthesis Imbalance in handler-case
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*Problem:* Using =(condition (var) ...)= as error handler type caused "end of file" errors because =condition= is not a valid error type in =handler-case=, and =t= is also invalid.
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*Solution:* Use =error= as the catch-all error type:
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#+BEGIN_EXAMPLE
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;; WRONG:
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(handler-case
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(risky-operation)
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(t () ...)) ; t is not valid
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(condition () ...)) ; condition needs to be a type
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;; CORRECT:
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(handler-case
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(risky-operation)
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(error () ; error is the correct catch-all type
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(format t "Error occurred~%")
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nil))
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#+END_EXAMPLE
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*** Challenge 5: let* Structure with handler-case
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*Problem:* When adding =handler-case= with a =progn= wrapper, the =let*= binding was closed before the =when= block that used its variables, causing "end of file" errors.
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*Solution:* Keep =let*= as the main form and put all logic inside it:
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#+BEGIN_EXAMPLE
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;; WRONG:
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(handler-case
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(progn
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(let* ((url "...")
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(response (fetch url)))
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(when response ...))) ; let* closed too early!
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(error () nil))
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;; CORRECT:
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(let* ((url "...")
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(response (fetch url)))
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(when response
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...)) ; All logic inside let*
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#+END_EXAMPLE
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*** Challenge 6: Icecast Listener Count Aggregation
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*Problem:* Function only checked =/asteroid.mp3= mount point, missing listeners on =/asteroid.aac= and =/asteroid-low.mp3= streams.
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*Solution:* Modified =icecast-now-playing= function in =frontend-partials.lisp= to loop through all three mount points and aggregate listener counts:
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#+BEGIN_EXAMPLE
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(let ((total-listeners 0))
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(dolist (mount '("/asteroid\\.mp3" "/asteroid\\.aac" "/asteroid-low\\.mp3"))
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(let ((match-pos (cl-ppcre:scan (format nil "<source mount=\"~a\">" mount) xml-string)))
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(when match-pos
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(let* ((source-section (subseq xml-string match-pos ...))
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(listenersp (cl-ppcre:all-matches "<listeners>" source-section)))
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(when listenersp
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(let ((count (parse-integer (cl-ppcre:regex-replace-all
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".*<listeners>(.*?)</listeners>.*"
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source-section "\\1")
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:junk-allowed t)))
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(incf total-listeners count)))))))
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total-listeners)
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#+END_EXAMPLE
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*Additional Changes to frontend-partials.lisp:*
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- Fixed stray =^= character in =(in-package :asteroid)= form
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- Added error handler to =define-api asteroid/partial/now-playing= endpoint to catch errors gracefully
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- Added debug logging to track Icecast stats fetching and parsing
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- Removed problematic error variable usage in error handlers (see Challenge 3)
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*** Success Metrics
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- player.lisp compiles without errors
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- All player functionality works (play, pause, queue, playlists)
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- Now Playing section displays correctly with live track information
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- Listener count aggregates across all three streams
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- No JavaScript runtime errors in browser console
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- No server-side Lisp errors
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** Summary of Key ParenScript Patterns
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1. *Async/Await*: Use promise chains with =.then()= instead
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2. *Modulo*: Use =rem= instead of =%=
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3. *Global Variables*: Use =defvar= with asterisks: =*variable-name*=
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4. *String Concatenation*: Use =+= operator
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5. *Property Access*: Use =ps:getprop= for dynamic/hyphenated properties
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6. *Object Creation*: Use =ps:create= with keyword arguments
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7. *Array Methods*: Use =ps:chain= for method chaining
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8. *Route Interception*: Use =cond= in static route handler
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9. *Compile at Load Time*: Store compiled JS in =defparameter=
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10. *Return Pre-compiled String*: Function just returns the parameter value
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11. *Array Push*: Use =(setf (aref array (ps:@ array length)) item)= instead of =push=
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12. *Not Equal*: Use =(not (== ...))= instead of =!==
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13. *Error Handlers*: Don't use error variable names in =format= statements; use =error= type for catch-all
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14. *Parenthesis Balance*: Keep =let*= as main form, don't wrap with =progn= inside =handler-case=
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** Final Status (2025-11-07)
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✅ *ALL JAVASCRIPT FILES SUCCESSFULLY CONVERTED TO PARENSCRIPT*
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The ParenScript migration is complete! All client-side JavaScript is now generated from Common Lisp code. The application maintains 100% of its original functionality while using a single language (Lisp) for both frontend and backend.
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Files converted:
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- =auth-ui.js= → =parenscript/auth-ui.lisp=
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- =front-page.js= → =parenscript/front-page.lisp=
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- =profile.js= → =parenscript/profile.lisp=
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- =users.js= → =parenscript/users.lisp=
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- =player.js= → =parenscript/player.lisp=
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- =admin.js= → =parenscript/admin.lisp=
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The experiment was a success. We can now maintain the entire Asteroid Radio codebase in Common Lisp.
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