# This file is part of Tryton.  The COPYRIGHT file at the top level of
# this repository contains the full copyright notices and license terms.
import base64
import html
import mimetypes
import os
import posixpath
import re
from pathlib import Path
from urllib.parse import unquote

from trytond.model import ModelSingleton, ModelSQL, ModelView, fields
from trytond.transaction import Transaction


DOCUMENTATION_ROOT = Path(__file__).with_name('process_documentation')
MARKDOWN_LINK = re.compile(r'(!?)\[([^\]]*)\]\(([^)]+)\)')
HTML_IMAGE_SOURCE = re.compile(
    r'(<img\b[^>]*\bsrc=)(["\'])([^"\']+)(\2)', re.IGNORECASE)


class ProcessDocumentation(ModelSingleton, ModelSQL, ModelView):
    "Process Documentation"
    __name__ = 'purchase_trade.process.documentation'

    content = fields.Function(fields.Text('Content'), 'get_content')

    @staticmethod
    def default_content():
        return _html_content()

    def get_content(self, name):
        return _html_content()


def _html_content():
    html_file = Transaction().context.get('process_documentation_html')
    if html_file:
        return _html_file_content(html_file)

    document = HTML_TEMPLATE % {
        'content': _documentation_content(),
        }
    return IFRAME_TEMPLATE % {
        'document': html.escape(document, quote=True),
        }


def _html_file_content(filename):
    path = (DOCUMENTATION_ROOT / Path(*filename.split('/'))).resolve()
    root = DOCUMENTATION_ROOT.resolve()
    common_path = os.path.commonpath([str(root), str(path)])
    if path != root and common_path == str(root):
        if path.exists() and path.is_file() and path.suffix.lower() == '.html':
            document = path.read_text(encoding='utf-8')
            document = _inline_html_assets(document, _relative_name(path))
            return IFRAME_TEMPLATE % {
                'document': html.escape(document, quote=True),
                }
    return _html_error('Documentation page not found: %s' % filename)


def _inline_html_assets(document, current_file):
    def replace(match):
        prefix, quote, source, suffix = match.groups()
        resolved = _resolve_link(current_file, source)
        if resolved.startswith(('http://', 'https://', 'data:', 'mailto:')):
            return match.group(0)

        data_uri = _asset_data_uri(resolved)
        if not data_uri:
            return match.group(0)
        return '%s%s%s%s' % (prefix, quote, html.escape(data_uri, quote=True),
            suffix)

    return HTML_IMAGE_SOURCE.sub(replace, document)


def _html_error(message):
    document = HTML_TEMPLATE % {
        'content': '<p>%s</p>' % html.escape(message),
        }
    return IFRAME_TEMPLATE % {
        'document': html.escape(document, quote=True),
        }


def _documentation_content():
    sections = []
    index = DOCUMENTATION_ROOT / 'README.md'
    if index.exists():
        sections.append(_render_page(index))

    for path in sorted(DOCUMENTATION_ROOT.rglob('*.md')):
        if path == index:
            continue
        sections.append(_render_page(path))
    return '\n'.join(sections)


def _render_page(path):
    relative_name = _relative_name(path)
    markdown = path.read_text(encoding='utf-8')
    return '<section id="%s">%s</section>' % (
        _anchor(relative_name), _markdown_to_html(markdown, relative_name))


def _relative_name(path):
    return path.relative_to(DOCUMENTATION_ROOT.resolve()).as_posix()


def _anchor(filename):
    return 'doc-' + re.sub(r'[^a-zA-Z0-9_-]+', '-', filename)


def _resolve_link(current_file, target):
    if target.startswith(('#', 'http://', 'https://', 'mailto:')):
        return target
    target = unquote(target).replace('\\', '/')
    current_dir = posixpath.dirname(current_file)
    return posixpath.normpath(posixpath.join(current_dir, target)).lstrip('/')


def _asset_data_uri(filename):
    path = (DOCUMENTATION_ROOT / Path(*filename.split('/'))).resolve()
    root = DOCUMENTATION_ROOT.resolve()
    common_path = os.path.commonpath([str(root), str(path)])
    if path != root and common_path == str(root):
        if path.exists() and path.is_file():
            mimetype = mimetypes.guess_type(str(path))[0]
            mimetype = mimetype or 'application/octet-stream'
            data = base64.b64encode(path.read_bytes()).decode('ascii')
            return 'data:%s;base64,%s' % (mimetype, data)


def _inline(markdown, current_file):
    parts = []
    last = 0
    for match in MARKDOWN_LINK.finditer(markdown):
        parts.append(html.escape(markdown[last:match.start()]))
        is_image, label, target = match.groups()
        resolved = _resolve_link(current_file, target)
        label = html.escape(label)

        if is_image:
            source = _asset_data_uri(resolved)
            if source:
                parts.append('<img src="%s" alt="%s"/>' % (
                        html.escape(source, quote=True), label))
            else:
                parts.append(label)
        elif resolved.endswith('.md'):
            parts.append(_internal_link(_anchor(resolved), label))
        elif resolved.startswith('#'):
            parts.append(_internal_link(resolved.lstrip('#'), label))
        elif resolved.startswith(('http://', 'https://', 'mailto:')):
            parts.append('<a href="%s">%s</a>' % (
                    html.escape(resolved, quote=True), label))
        else:
            parts.append(html.escape(match.group(0)))
        last = match.end()
    parts.append(html.escape(markdown[last:]))
    return ''.join(parts)


def _markdown_to_html(markdown, current_file):
    body = []
    table = []
    in_list = False

    def close_list():
        nonlocal in_list
        if in_list:
            body.append('</ul>')
            in_list = False

    def flush_table():
        nonlocal table
        if table:
            close_list()
            body.append(_render_table(table, current_file))
            table = []

    for line in markdown.splitlines():
        stripped = line.strip()
        if stripped.startswith('|') and stripped.endswith('|'):
            table.append(stripped)
            continue

        flush_table()
        if not stripped:
            close_list()
            continue

        if stripped.startswith('#'):
            close_list()
            level = len(stripped) - len(stripped.lstrip('#'))
            level = min(level, 6)
            title = stripped[level:].strip()
            body.append('<h%d>%s</h%d>' % (
                    level, _inline(title, current_file), level))
        elif stripped.startswith('- '):
            if not in_list:
                body.append('<ul>')
                in_list = True
            body.append('<li>%s</li>' % _inline(
                    stripped[2:].strip(), current_file))
        else:
            close_list()
            body.append('<p>%s</p>' % _inline(stripped, current_file))

    flush_table()
    close_list()

    if current_file != 'README.md':
        body.insert(
            0, '<p>%s</p>' % _internal_link('doc-README-md', 'Back to index'))
    return '\n'.join(body)


def _internal_link(anchor, label):
    anchor = html.escape(anchor, quote=True)
    return '<a href="#%s" data-doc-target="%s">%s</a>' % (
        anchor, anchor, label)


def _render_table(lines, current_file):
    rows = [
        [cell.strip() for cell in line.strip('|').split('|')]
        for line in lines
        ]
    header = rows[0] if rows else []
    data = rows[1:]
    if data and all(set(cell) <= {'-', ':'} for cell in data[0]):
        data = data[1:]

    output = ['<table>', '<thead><tr>']
    for cell in header:
        output.append('<th>%s</th>' % _inline(cell, current_file))
    output.append('</tr></thead><tbody>')
    for row in data:
        output.append('<tr>')
        for cell in row:
            output.append('<td>%s</td>' % _inline(cell, current_file))
        output.append('</tr>')
    output.append('</tbody></table>')
    return ''.join(output)


IFRAME_TEMPLATE = '''<iframe srcdoc="%(document)s"
    style="border: 0; height: calc(100vh - 160px); min-height: 760px; width: 100%%;"
    title="Tradon Processes"></iframe>
'''


HTML_TEMPLATE = '''<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
    <style>
        body {
            color: #1f2933;
            font-family: Arial, sans-serif;
            line-height: 1.5;
            margin: 0;
            padding: 24px;
        }
        a {
            color: #0b63ce;
            text-decoration: none;
        }
        a:hover {
            text-decoration: underline;
        }
        table {
            border-collapse: collapse;
            margin: 16px 0;
            width: 100%%;
        }
        th,
        td {
            border: 1px solid #d7dde5;
            padding: 8px 10px;
            text-align: left;
            vertical-align: top;
        }
        th {
            background: #f3f6f9;
        }
        img {
            height: auto;
            max-width: 100%%;
        }
    </style>
</head>
<body>
    <main>%(content)s</main>
    <script>
        document.addEventListener('click', function(event) {
            var link = event.target.closest('a[data-doc-target]');
            if (!link) {
                return;
            }
            var target = document.getElementById(link.dataset.docTarget);
            if (!target) {
                return;
            }
            event.preventDefault();
            target.scrollIntoView({block: 'start'});
        });
    </script>
</body>
</html>
'''