#!/bin/bash

# Download and compare text from two URLs in parallel
# License: LGPLv2
# Author:
#    http://www.pixelbeat.org/

# Be careful to quote URLs appropriately like:
#  urldiff 'URL1' 'URL2'

# Follow redirections and only show errors as generally
# text for comparison is relatively small
curl --version &>/dev/null && global URLGET := '"curl -sS -L'" || global URLGET := '"wget -nv -O-'"

# Download in parallel and compare
idiff $[$URLGET $1] $[$URLGET $2]

# Note it would be better to avoid diffing if one of the URLGETs fail,
# though that would involve manipulating named pipes directly,
# so KISS and rely on error messages and only addition of lines,
# to indicate (partial) errors.
(CommandList
  children: [
    (Sentence child:(C {(curl)} {(--version)}) terminator:<Op_Amp "&">)
    (AndOr
      children: [
        (SimpleCommand
          redirects: [(Redir op_id:Redir_Great fd:-1 arg_word:{(/dev/null)} spids:[35])]
        )
        (AndOr
          children: [
            (Assignment
              keyword: Assign_None
              pairs: [
                (assign_pair
                  lhs: (LhsName name:URLGET)
                  op: Equal
                  rhs: {(DQ ("curl -sS -L"))}
                  spids: [40]
                )
              ]
              spids: [40]
            )
            (Assignment
              keyword: Assign_None
              pairs: [
                (assign_pair
                  lhs: (LhsName name:URLGET)
                  op: Equal
                  rhs: {(DQ ("wget -nv -O-"))}
                  spids: [47]
                )
              ]
              spids: [47]
            )
          ]
          op_id: Op_DPipe
        )
      ]
      op_id: Op_DAmp
    )
    (C {(idiff)} 
      {
        (CommandSubPart
          command_list: 
            (CommandList
              children: [(C {($ VSub_Name "$URLGET")} {(DQ ($ VSub_Number "$1"))})]
            )
          left_token: <Left_ProcSubIn "<(">
          spids: [58 64]
        )
      } 
      {
        (CommandSubPart
          command_list: 
            (CommandList
              children: [(C {($ VSub_Name "$URLGET")} {(DQ ($ VSub_Number "$2"))})]
            )
          left_token: <Left_ProcSubIn "<(">
          spids: [66 72]
        )
      }
    )
  ]
)