#!/usr/bin/python

"""Python module for generating .ninja files.

Note that this is emphatically not a required piece of Ninja; it's
just a helpful utility for build-file-generation systems that already
use Python.
"""

import re
import textwrap

def escape_path(word):
    return word.replace('$ ', '$$ ').replace(' ', '$ ').replace(':', '$:')

class Writer(object):
    def __init__(self, output, width=78):
        self.output = output
        self.width = width

    def newline(self):
        self.output.write('\n')

    def comment(self, text):
        for line in textwrap.wrap(text, self.width - 2):
            self.output.write('# ' + line + '\n')

    def variable(self, key, value, indent=0):
        if value is None:
            return
        if isinstance(value, list):
            value = ' '.join(filter(None, value))  # Filter out empty strings.
        self._line('%s = %s' % (key, value), indent)

    def pool(self, name, depth):
        self._line('pool %s' % name)
        self.variable('depth', depth, indent=1)

    def rule(self, name, command, description=None, depfile=None,
             generator=False, pool=None, restat=False, rspfile=None,
             rspfile_content=None, deps=None):
        self._line('rule %s' % name)
        self.variable('command', command, indent=1)
        if description:
            self.variable('description', description, indent=1)
        if depfile:
            self.variable('depfile', depfile, indent=1)
        if generator:
            self.variable('generator', '1', indent=1)
        if pool:
            self.variable('pool', pool, indent=1)
        if restat:
            self.variable('restat', '1', indent=1)
        if rspfile:
            self.variable('rspfile', rspfile, indent=1)
        if rspfile_content:
            self.variable('rspfile_content', rspfile_content, indent=1)
        if deps:
            self.variable('deps', deps, indent=1)

    def build(self, outputs, rule, inputs=None, implicit=None, order_only=None,
              variables=None):
        outputs = as_list(outputs)
        out_outputs = [escape_path(x) for x in outputs]
        all_inputs = [escape_path(x) for x in as_list(inputs)]

        if implicit:
            implicit = [escape_path(x) for x in as_list(implicit)]
            all_inputs.append('|')
            all_inputs.extend(implicit)
        if order_only:
            order_only = [escape_path(x) for x in as_list(order_only)]
            all_inputs.append('||')
            all_inputs.extend(order_only)

        self._line('build %s: %s' % (' '.join(out_outputs),
                                     ' '.join([rule] + all_inputs)))

        if variables:
            if isinstance(variables, dict):
                iterator = iter(variables.items())
            else:
                iterator = iter(variables)

            for key, val in iterator:
                self.variable(key, val, indent=1)

        return outputs

    def include(self, path):
        self._line('include %s' % path)

    def subninja(self, path):
        self._line('subninja %s' % path)

    def default(self, paths):
        self._line('default %s' % ' '.join(as_list(paths)))

    def _count_dollars_before_index(self, s, i):
        """Returns the number of '$' characters right in front of s[i]."""
        dollar_count = 0
        dollar_index = i - 1
        while dollar_index > 0 and s[dollar_index] == '$':
            dollar_count += 1
            dollar_index -= 1
        return dollar_count

    def _line(self, text, indent=0):
        """Write 'text' word-wrapped at self.width characters."""
        leading_space = '  ' * indent
        while len(leading_space) + len(text) > self.width:
            # The text is too wide; wrap if possible.

            # Find the rightmost space that would obey our width constraint and
            # that's not an escaped space.
            available_space = self.width - len(leading_space) - len(' $')
            space = available_space
            while True:
                space = text.rfind(' ', 0, space)
                if (space < 0 or
                    self._count_dollars_before_index(text, space) % 2 == 0):
                    break

            if space < 0:
                # No such space; just use the first unescaped space we can find.
                space = available_space - 1
                while True:
                    space = text.find(' ', space + 1)
                    if (space < 0 or
                        self._count_dollars_before_index(text, space) % 2 == 0):
                        break
            if space < 0:
                # Give up on breaking.
                break

            self.output.write(leading_space + text[0:space] + ' $\n')
            text = text[space+1:]

            # Subsequent lines are continuations, so indent them.
            leading_space = '  ' * (indent+2)

        self.output.write(leading_space + text + '\n')

    def close(self):
        self.output.close()


def as_list(input):
    if input is None:
        return []
    if isinstance(input, list):
        return input
    return [input]


def escape(string):
    """Escape a string such that it can be embedded into a Ninja file without
    further interpretation."""
    assert '\n' not in string, 'Ninja syntax does not allow newlines'
    # We only have one special metacharacter: '$'.
    return string.replace('$', '$$')


def expand(string, vars, local_vars={}):
    """Expand a string containing $vars as Ninja would.

    Note: doesn't handle the full Ninja variable syntax, but it's enough
    to make configure.py's use of it work.
    """
    def exp(m):
        var = m.group(1)
        if var == '$':
            return '$'
        return local_vars.get(var, vars.get(var, ''))
    return re.sub(r'\$(\$|\w*)', exp, string)