errors.ktg

; `attempt` is a pipeline dialect for composing steps that
; can fail.  Each step threads the previous result through
; `it`.  Errors short-circuit to a matching `catch` arm.

; --- source + then pipeline ---
result: attempt [
  source ["  Hello, World  "]
  then   [trim it]
  then   [lowercase it]
  then   [split it ", "]
]
probe result                       ; ["hello" "world"]

; --- without source, attempt is a reusable function ---
clean: attempt [
  when [not empty? it]
  then [trim it]
  then [lowercase it]
]
print clean "  HEY  "              ; hey

; --- catch by error kind ---
recover: attempt [
  source [error 'parse "bad input"]
  catch 'parse [
    rejoin ["recovered: " error]
  ]
  fallback ["unknown failure"]
]
print recover                      ; recovered: bad input

; --- fallback for anything uncaught ---
loud-parse: attempt [
  source [error 'other "boom"]
  catch 'parse ["parse error"]
  fallback ["generic failure"]
]
print loud-parse                   ; generic failure

; --- retries ---
; Counter closure simulates a flaky operation that fails
; twice then succeeds.
attempts: 0
flaky: does [
  attempts: attempts + 1
  either attempts < 3 [
    error 'network "try again"
  ] [
    "success"
  ]
]

out: attempt [
  source [flaky]
  retries 3
  catch 'network ["gave up"]
]
print out                          ; success
print attempts                     ; 3