Create a new interactive_t helper class

The purpose of this class is much like Emacs' (interactive) form: it
allows a value expression function to declare exactly how many
arguments, and of what type, it intends to receive.  It then offers
type-safe access to theese arguments in a consistent manner.

An example value expression function definition in C++:

    value_t fn_foo(call_scope_t& scope) {
      // We expect a string, an integer, and an optional date
      interactive_t args(scope, "sl&d");

      std::cout << "String  = " << args.get<string>(0)
                << "Integer = " << args.get<long>(1) << std::endl;

      if (args.has(2)) // was a date provided?
        std::cout << "Date    = " << args.get<date_t>(2) << std::endl;

      return NULL_VALUE;
    }

There is also an in_context_t<T> template, which finds the context type
T in the current scope hierarchy.  The in_context_t then also acts as a
smart pointer to reference this context object, in addition to serving
the same duty as interactive_t.  This combination of intent is solely
for the sake of brevity.

    value_t fn_bar(call_scope_t& scope) {
      in_context_t<account_t> env(scope, "sl&d");
      std::cout << "Account name = " << env->fullname()
                << "String arg   = " << env.get<string>(0)
                << std::endl;
      return NULL_VALUE;
    }

As you can see here, 'env' acts as a smart pointer to the required
context, and an object to extract the typed arguments.

1 files changed, 184 insertions, 0 deletions

diff --git a/src/interactive.cc b/src/interactive.cc
new file mode 100644
index 00000000..3e2d6d5e
--- /dev/null
+++ b/src/interactive.cc
@@ -0,0 +1,184 @@
+/*
+ * Copyright (c) 2003-2009, John Wiegley.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of New Artisans LLC nor the names of its
+ *   contributors may be used to endorse or promote products derived from
+ *   this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "interactive.h"
+
+namespace ledger {
+
+void interactive_t::verify_arguments() const
+{
+  value_t::sequence_t::const_iterator i;
+
+  const char *	  p	    = spec.c_str();
+  const char *	  label	    = "unknown";
+  bool		  wrong_arg = false;
+  bool		  dont_skip = false;
+  bool		  optional  = *p == '&';
+  bool		  exit_loop = *p == '*';
+  std::size_t	  offset    = 1;
+  bool		  is_seq    = args.value().is_sequence();
+  const value_t * next_arg  = NULL;
+  string	  vlabel;
+
+  if (is_seq) {
+    i = args.begin();
+    if (i != args.end())
+      next_arg = &(*i);
+  }
+  else if (! args.value().is_null()) {
+    next_arg = &args.value();
+  }
+
+  for (; ! wrong_arg && ! exit_loop && *p && next_arg; p++) {
+    switch (*p) {
+    case 'a':
+      label = "an amount";
+      wrong_arg = (! next_arg->is_long() &&
+		   ! next_arg->is_amount() &&
+		   ! next_arg->is_balance());
+      break;
+    case 'b':
+      label = "a boolean";
+      wrong_arg = false;	// booleans are converted
+      break;
+    case 'd':
+      label = "a date";
+      wrong_arg = ! next_arg->is_date();
+      break;
+    case 'i':
+    case 'l':
+      label = "an integer";
+      if (next_arg->is_long() ||
+	  (next_arg->is_amount() &&
+	   ! next_arg->as_amount().has_commodity())) {
+	wrong_arg = false;
+      }
+      else if (next_arg->is_string()) {
+	wrong_arg = false;
+	for (const char * q = next_arg->as_string().c_str(); *q; q++) {
+	  if (! std::isdigit(*q) && *q != '-') {
+	    wrong_arg = true;
+	    break;
+	  }
+	}
+      }
+      else {
+	wrong_arg = true;
+      }
+      break;
+    case 'm':
+      label = "a regex";
+      wrong_arg = ! next_arg->is_mask();
+      break;
+    case 's':
+      label = "a string";
+      wrong_arg = ! next_arg->is_string();
+      break;
+    case 't':
+      label = "a date or time";
+      wrong_arg = (! next_arg->is_date() &&
+		   ! next_arg->is_datetime());
+      break;
+    case 'v':
+      label = "any value";
+      wrong_arg = false;
+      break;
+    case 'P':
+      label = "a pointer";
+      wrong_arg = ! next_arg->is_pointer();
+      break;
+    case 'S':
+      label = "a sequence";
+      wrong_arg = ! next_arg->is_sequence();
+      break;
+    case '&':
+      optional = true;
+      dont_skip = true;
+      break;
+    case '*':
+      optional  = true;
+      exit_loop = true;
+      dont_skip = true;
+      break;
+    }
+
+    if (wrong_arg)
+      vlabel = next_arg->label();
+
+    if (! dont_skip) {
+      if (is_seq) {
+	if (++i != args.end()) {
+	  next_arg = &(*i);
+	  offset++;
+	} else {
+	  next_arg = NULL;
+	}
+      } else {
+	next_arg = NULL;
+      }
+    }
+    dont_skip = false;
+  }
+
+  if (*p == '&' || *p == '*')
+    optional = true;
+
+  if (wrong_arg) {
+    throw_(std::logic_error,
+	   "Expected " << label << " for argument " << offset
+	   << ", but received " << vlabel);
+  }
+  else if (! optional && ! next_arg) {
+    throw_(std::logic_error, "Too few arguments to function");
+  }
+  else if (! *p && next_arg) {
+    throw_(std::logic_error, "Too many arguments to function");
+  }
+}
+
+string join_args(call_scope_t& args)
+{
+  std::ostringstream buf;
+  bool first = true;
+
+  for (std::size_t i = 0; i < args.size(); i++) {
+    if (first) {
+      buf << args[i];
+      first = false;
+    } else {
+      buf << ' ' << args[i];
+    }
+  }
+
+  return buf.str();
+}
+
+} // namespace ledger