#!/usr/bin/python3

import os.path
import re
import sys
import tempfile
from optparse import OptionParser


"""
Poorly convert some cheetah template code to jinja

This is NOT a full or accurate conversion, it is a set of simple
tranformations that reduce some of the manual work.

Always review the changes.
Always review the changes.
"""


def main():
    global subs
    global options
    parser = OptionParser(usage="%prog <filename>")
    parser.add_option('-w', '--write', action='store_true', help='write changes to file')
    options, args = parser.parse_args()
    options.args = args

    if len(args) != 1:
        error('Please specify one template')
    fn = args[0]
    handle_file(fn)


def handle_file(fn):
    outp = None
    if options.write:
        dirname = os.path.dirname(fn)
        basename = os.path.basename(fn)
        outfile = tempfile.NamedTemporaryFile(dir=dirname, mode='wt', prefix=f'_{basename}', delete=False)
        with outfile as outp:
            _handle_file(fn, outp)
        os.replace(outfile.name, fn)
        print(f'Wrote {fn}')
    else:
        _handle_file(fn, outp)


def _handle_file(fn, outp):
    with open(fn, 'rt') as fp:
        for lineno, line in enumerate(fp):
            line = handle_line(lineno, line, outp)
            if line is not None and outp is not None:
                outp.write(line)


def handle_line(lineno, line, outp):
    orig = line
    matches = 0
    skip = False
    rules = list(SUBS)
    while rules:
        prog, repl = rules.pop(0)
        last = line
        if repl == SKIP:
            m = prog.search(line)
            if m:
                print(f'{lineno}: Matched skip pattern {prog.pattern!r}')
                print(line, end='')
                skip = True
                line = orig
                break
            continue
        elif repl == DROP:
            m = prog.search(line)
            if m:
                print(f'{lineno}: Matched DROP pattern {prog.pattern!r}')
                print(line, end='')
                return None
        elif repl == BREAK:
            m = prog.search(line)
            if m:
                print(f'{lineno}: Matched BREAK pattern {prog.pattern!r}')
                print(line, end='')
                break
        elif isinstance(repl, Jump):
            # forget remaing rules and use target rules from here
            m = prog.search(line)
            if m:
                rules = list(repl.target)
        else:
            line, n = prog.subn(repl, line)
            if n:
                matches += n
                print(f'{lineno}: Matched {prog.pattern!r} (count: {n})')
    if matches:
        print(f'Made {matches} substitutions for line {lineno}')
        print(f'ORIG: {orig}', end='')
        print(f' NEW: {line}')
    return collapse(line)


def rules(subs):
    # compile subs
    return [(re.compile(pat, flags), repl) for pat, repl, flags in subs]


class Jump:
    # jump to new set of substitutions
    def __init__(self, target):
        self.target = target


SKIP = ('skip subs for this line',)
DROP = ('drop line',)
BREAK = ('stop subs checks for this line',)
STATE = rules([
    # subrules for some line statements
    [r'[$]', '', 0],
    [r'len\(([\w.$]+)\)', r'(\1 |length)', 0 ],
])
SUBS = rules([
    # [pattern, replacement, flags]
    [r'util.(toggleOrder|rowToggle|sortImage|passthrough_except|passthrough|authToken)\b', r'util.\g<1>2', 0],
    [r'(#include .*)header.chtml', r'\1header2.chtml', 0],
    [r'(#include .*)footer.chtml', r'\1footer2.chtml', 0],
    [r'^#import', DROP, 0],
    [r'^#from .* import', DROP, 0],
    [r'^\s*#(if|for|elif|set)', Jump(STATE), 0],
    [r'#end if', r'#endif', 0],
    [r'#end for', r'#endfor', 0],
    [r'[(][$]self, ', r'(', 0 ],
    [r'\([$]self\)', r'()', 0 ],
    [r'len\(([\w.$]+)\)', r'(\1 |length)', 0 ],
    [r'[$](([\w.]+)[(][^()]*[)])', r'{{ \1 }}', 0 ],
    [r'${\s*([^{}]+)\s*}', r'{{ \1 }}', 0 ],
    [r'#echo ([^#]+)#', r'{{ \1 }}', 0 ],
    [r'#if ([^#]+) then ([^#]+) else ([^#]+)\s*#', r'{{ \2 if \1 else \3 }}', 0 ],
    [r'''[$]([\w.]+)\['(\w+)'\]''', r'{{ \1.\2 }}', 0],
    [r'''[$]([\w.]+)\["(\w+)"\]''', r'{{ \1.\2 }}', 0],
    [r'[$]([\w.]+)[([]', SKIP, 0],
    [r'^(\s*)#attr ', r'\1#set ', 0],
    [r'^\s*#', BREAK, 0],
    [r'[$]([\w.]+)', r'{{ \1 }}', 0],
])


def error(msg):
    print(msg)
    sys.exit(1)


BRACES = re.compile(r'({{ | }})')

def collapse(line):
    """Collapse nested double braces"""
    tokens = BRACES.split(line)

    depth = 0
    tokens2 = []
    for tok in tokens:
        if tok == '{{ ':
            # only keep braces at the outer layer
            if depth == 0:
                tokens2.append(tok)
            depth += 1
        elif tok == ' }}':
            depth -= 1
            if depth < 0:
                warning("Brace  mismatch. Can't collapse")
                break
            elif depth == 0:
                # only keep braces at the outer layer
                tokens2.append(tok)
        else:
            # keep everything else
            tokens2.append(tok)

    if depth < 0:
        warning('Unexpected }}')
        return line
    elif depth > 0:
        warning('Missing }}')
        return line
    else:
        return ''.join(tokens2)


if __name__ == '__main__':
    main()