cal: process lines into nested representation

2 files changed, 196 insertions, 29 deletions

diff --git a/cal.lua b/cal.lua
index bb48c68..b7f3a9d 100755..100644
--- a/cal.lua
+++ b/cal.lua
@@ -1,10 +1,11 @@
-#!/usr/bin/env lua
 --[[--
 
     RFC2445 parser / printer.
 
 --]]--
 
+local pcall         = pcall
+
 local io            = require "io"
 local ioopen        = io.open
 local iostdin       = io.stdin
@@ -15,6 +16,7 @@ local mathmin       = math.min
 
 local string        = require "string"
 local stringformat  = string.format
+local stringlower   = string.lower
 local stringsub     = string.sub
 
 local table         = require "table"
@@ -42,7 +44,15 @@ local errorln       = mk_out ("stderr", 0, true)
 local noiseln       = mk_out ("stderr", 1, true)
 local debugln       = mk_out ("stderr", 2, true)
 
-local fmt_calendar do
+--[[--
+
+  fmt_calendar_lines (cal) -> string
+  — take a flattened lines representation of a calendar and formats it into a
+  string
+
+--]]--
+
+local fmt_calendar_lines do
   local fold_rfc2445    = 75  --- B
   local fold_wsp        = " " --- could be tab as well
   local crlf            = "\r\n"
@@ -90,12 +100,13 @@ local fmt_calendar do
     return tableconcat (acc, newline)
   end
 
-  fmt_calendar = function (cal, fold, newline, i, acc)
+  fmt_calendar_lines = function (cal, fold, newline, i, acc)
+    print("fmt_calendar_lines()", cal, fold, newline, i, acc)
     if i == nil then
-      return fmt_calendar (cal,
-                           fold or fold_rfc2445,
-                           newline or crlf,
-                           1, { })
+      return fmt_calendar_lines (cal,
+                                 fold or fold_rfc2445,
+                                 newline or crlf,
+                                 1, { })
     end
     if i > #cal then return tableconcat (acc, newline) end
 
@@ -108,7 +119,7 @@ local fmt_calendar do
 
     acc [#acc + 1] = line
 
-    return fmt_calendar (cal, fold, newline, i + 1, acc)
+    return fmt_calendar_lines (cal, fold, newline, i + 1, acc)
   end
 end
 
@@ -128,7 +139,14 @@ local fmt_calendar_params do
   end
 end
 
-local parse_calendar do
+--[[--
+
+  parse_calendar_lines(str)
+  — dissect a calendar *str* into lines, unfolding the input if necessary
+
+--]]--
+
+local parse_calendar_lines do
   local lpeg            = require "lpeg"
   local lpegmatch       = lpeg.match
   local C               = lpeg.C
@@ -269,8 +287,8 @@ local parse_calendar do
     return lpegmatch (p_skip_line, raw, pos0)
   end
 
-  parse_calendar = function (raw, pos0, acc, consumed, nline, nskipped)
-    if pos0 == nil then return parse_calendar (raw, 1, { }, 0, 1, 0) end
+  parse_calendar_lines = function (raw, pos0, acc, consumed, nline, nskipped)
+    if pos0 == nil then return parse_calendar_lines (raw, 1, { }, 0, 1, 0) end
 
     local ok, pos1, name, params, value = parse_content_line (raw, pos0)
 
@@ -291,22 +309,151 @@ local parse_calendar do
                        , name = name, params = params, value = value }
     end
 
-    return parse_calendar (raw, pos1, acc, consumed + (pos1 - pos0), nline + 1,
-                           nskipped)
+    return parse_calendar_lines (raw, pos1, acc, consumed + (pos1 - pos0),
+                                 nline + 1, nskipped)
   end
-end
+end --- [parse_calendar_lines]
 
-local loaddata = function (fname)
-  local fh = ioopen (fname, "r")
+local calendar_of_lines do
+  --[[--
+
+    line handlers either return *true*, new line index, data or
+    *false*, new line index and an error message.
+
+  --]]--
+  local process
+  
+  process = function (lines, n, acc)
+    if n == nil then n = 1 end
+
+    if n > #lines then
+      if acc == nil then
+        return false, n, "no usable input"
+      end
+      return true, n, acc
+    end
+
+    local cur = lines [n]
+    if cur == nil then
+      return false, n, "hit garbage line"
+    end
+
+    local curname  = stringlower (cur.name)
+    local curvalue = cur.value
+
+    if curname == "begin" then
+      if stringlower (curvalue) == "vcalendar" then
+        acc = { value = { } }
+      end
 
-  if fh == nil then
-    error ("could not open file " .. fname .. " for reading")
+      local ok, nn, ret = process (lines, n + 1,
+                                   { kind   = "scope"
+                                   , name   = curvalue
+                                   , params = cur.params
+                                   , value  = { }
+                                   })
+      if not ok then
+        return false, nn, stringformat ("bad nested content in “%s” scope: %s",
+                                        curvalue, ret)
+      end
+      --- parsing successful, append to current elements and continue with
+      --- the next line
+      acc.value [#acc.value + 1] = ret
+      return process (lines, nn, acc)
+    end
+
+    if curname == "end" then
+      if curvalue ~= acc.name then
+        return false, n, stringformat ("scope mismatch: \z
+                                        expecting “%s”, got “%s”",
+                                       n, acc.kind, curvalue)
+      end
+      --- closing the current scope, return accu
+      return true, n + 1, acc
+    end
+
+    acc.value [#acc.value + 1] = { kind   = "other"
+                                 , name   = curname
+                                 , value  = curvalue
+                                 , params = cur.params
+                                 }
+
+    return process (lines, n + 1, acc)
   end
 
-  local ret = fh:read ("*a")
-  fh:close ()
+  calendar_of_lines = function (lines)
+    local ok, n, components = process (lines)
+    if not ok then
+      return error (stringformat ("error at index %d: %s", n, components))
+    end
+    return components
+  end
+end --- [calendar_of_lines]
+
+
+--[[--
+
+  lines_of_calendar (cal) -> bool, lines
+  — takes a structured calendar and returns a flattened representation of lines
+
+--]]--
+
+local lines_of_calendar do
+
+  lines_of_calendar = function (cal, n, acc)
+    if n == nil then return lines_of_calendar (cal, 1, { }) end
+
+    local cur = cal [n]
+    if cur == nil then
+      return false, stringformat ("bad calendar object at index %d", n)
+    end
+
+    local curkind  = cur.kind
+    local curname  = stringupper (cur.name)
+    local curvalue = cur.value
+
+    if curkind == "scope" then
+      acc [#acc + 1] = { name = "BEGIN", value = curvalue }
+      local ok
+      ok, acc = lines_of_calendar (cal, n, acc)
+      if not ok then
+        return false, stringformat ("bad calendar component at index %d \z
+                                     inside “%s” scope: %s",
+                                    n, cur.value, acc)
+      end
+      acc [#acc + 1] = { name = "END", value = curvalue }
+
+      return lines_of_calendar (cal, n + 1, acc)
+    end
 
-  return ret
+    if curkind == "other" then
+      acc [#acc + 1] = { name  = curname
+                       , value = curvalue
+                       , prams = cur.params
+                       }
+      return lines_of_calendar (cal, n + 1, acc)
+    end
+
+    return false, stringformat ("invalid object kind “%s” at index %d \z
+                                 in calendar object", curkind, n)
+  end
+end --- [lines_of_calendar]
+
+--[[--
+
+  fmt_calendar (cal) -> string
+  — takes a structured calendar and emits a string in RFC2445 format.
+
+--]]--
+
+local fmt_calendar = function (cal)
+  local ok, lines = lines_of_calendar (cal)
+  if not ok then
+    return ok, stringformat ("failed to convert calendar to temporary line format: %s",
+                             lines)
+  end
+
+  return fmt_calendar_lines (lines)
 end
 
 -------------------------------------------------------------------------------
@@ -316,20 +463,30 @@ end
 local set_verbosity = function (n) verboselvl = n end
 
 local parse = function (raw)
-  local ok, obj = pcall (parse_calendar, raw)
-  return ok and obj
+  local ok, lines = pcall (parse_calendar_lines, raw)
+  if not ok then
+    return false, "failed to parse calendar object: " .. lines
+  end
+
+  local ok, obj = pcall (calendar_of_lines, lines)
+  if not ok then
+    return false, "failed to internalize calendar structure: " .. obj
+  end
+
+  return true, obj
 end
 
 local parse_handle = function (fh)
   local raw = fh:read ("*a")
-  return raw ~= nil and parse (raw)
+  if raw == nil then return nil end
+  return parse (raw)
 end
 
 local parse_file = function (fname)
   local fh = ioopen (fname, "r")
-  local cal = parse_handle (fh)
+  local ok, cal = parse_handle (fh)
   fh:close ()
-  return cal
+  return ok, cal
 end
 
 local parse_stdin = function ()
@@ -341,7 +498,10 @@ local format = function (cal, newline)
 end
 
 local output_handle = function (cal, fh)
-  local str = fmt_calendar (cal, nil, newline or "\n")
+  local ok, str = fmt_calendar (cal, nil, newline or "\n")
+  if not ok then
+    return false, str
+  end
   fh:write (str)
 end
 
diff --git a/inout.lua b/inout.lua
index ad1c23d..5878c16 100644..100755
--- a/inout.lua
+++ b/inout.lua
@@ -1,9 +1,16 @@
+#!/usr/bin/env lua
 local cal = require "cal"
 
 local main = function (argv)
-  local ok = cal.output (cal.parse_stdin ())
+  local ok, parsed = cal.parse_stdin ()
+  if not ok then
+    error ("error parsing input: " .. parsed)
+    return -1
+  end
 
-  return ok and 0 or -1
+  cal.output (parsed)
+
+  return 0
 end
 
 os.exit (main ())