# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Wiki internal links handling.
module wiki_links

import wiki_base
import markdown::wikilinks
import ordered_tree

redef class Nitiwiki
	# Looks up a WikiEntry by its `name`.
	#
	# Rules are:
	# 1. Looks in the current section
	# 2. Looks in the current section children
	# 3. Looks in the current section parent
	# 4. Looks up to wiki root
	#
	# Returns `null` if no article can be found.
	fun lookup_entry_by_name(context: WikiEntry, name: String): nullable WikiEntry do
		var section: nullable WikiEntry = context.parent or else context
		var res = section.as(not null).lookup_entry_by_name(name)
		if res != null then return res
		while section != null do
			if section.name == name then return section
			if section.children.has_key(name) then return section.children[name]
			section = section.parent
		end
		return null
	end

	# Looks up a WikiEntry by its `title`.
	#
	# Rules are:
	# 1. Looks in the current section
	# 2. Looks in the current section children
	# 3. Looks in the current section parent
	# 4. Looks up to wiki root
	#
	# Returns `null` if no article can be found.
	fun lookup_entry_by_title(context: WikiEntry, title: String): nullable WikiEntry do
		var section: nullable WikiEntry = context.parent or else context
		var res = section.as(not null).lookup_entry_by_title(title)
		if res != null then return res
		while section != null do
			if section.title.to_lower == title.to_lower then return section
			for child in section.children.values do
				if child.title.to_lower == title.to_lower then return child
			end
			section = section.parent
		end
		return null
	end

	# Looks up a WikiEntry by its `path`.
	#
	# Path can be relative from `context` like `context/entry`.
	# Or absolute like `/entry1/entry2`.
	#
	# Returns `null` if no article can be found.
	fun lookup_entry_by_path(context: WikiEntry, path: String): nullable WikiEntry do
		var entry = context.parent or else context
		var parts = path.split_with("/")
		if path.has_prefix("/") then
			entry = root_section
			if parts.is_empty then return root_section.index
			parts.shift
		end
		while not parts.is_empty do
			var name = parts.shift
			if name.is_empty then continue
			if entry.name == name then continue
			if not entry.children.has_key(name) then return null
			entry = entry.children[name]
		end
		return entry
	end

	# Trails between pages
	#
	# Trails are represented as a forest of entries.
	# This way it is possible to represent a flat-trail as a visit of a tree.
	var trails = new OrderedTree[WikiEntry]
end

redef class WikiEntry

	# Relative path to `self` from the target root_url
	fun href: String do return breadcrumbs.join("/")

	# Relative path to the directory `self` from the target root_url
	fun dir_href: String do return href.dirname

	# Relative path to the root url from `self`
	fun root_href: String do
		var root_dir = dir_href.relpath("")
		# Avoid issues if used as a macro just followed by a `/` (as with url prefix)
		if root_dir == "" then root_dir = "."
		return root_dir
	end

	# A relative `href` to `self` from the page `context`.
	#
	# Should be used to navigate between documents.
	fun href_from(context: WikiEntry): String
	do
		var res = context.dir_href.relpath(href)
		return res
	end

	# A relative hyperlink <a> to `self` from the page `context`.
	#
	# If `text` is not given, `title` will be used instead.
	fun a_from(context: WikiEntry, text: nullable Text): Writable
	do
		var title = title.html_escape
		if text == null then text = title else text = text.html_escape
		var href = href_from(context)
		return """<a href="{{{href}}}" title="{{{title}}}">{{{text}}}</a>"""
	end

	redef fun render do
		super
		if not is_dirty and not wiki.force_render then return
		render_sidebar_wikilinks
	end

	# Search in `self` then `self.children` if an entry has the name `name`.
	fun lookup_entry_by_name(name: String): nullable WikiEntry do
		if children.has_key(name) then return children[name]
		for child in children.values do
			var res = child.lookup_entry_by_name(name)
			if res != null then return res
		end
		return null
	end

	# Search in `self` then `self.children` if an entry has the title `title`.
	fun lookup_entry_by_title(title: String): nullable WikiEntry do
		for child in children.values do
			if child.title.to_lower == title.to_lower then return child
		end
		for child in children.values do
			var res = child.lookup_entry_by_title(title)
			if res != null then return res
		end
		return null
	end

	private var md_proc: NitiwikiMdProcessor is lazy do
		return new NitiwikiMdProcessor(wiki, self)
	end

	# Process wikilinks from sidebar.
	private fun render_sidebar_wikilinks do
		var blocks = sidebar.blocks
		for i in [0..blocks.length[ do
			blocks[i] = md_proc.process(blocks[i].to_s).write_to_string
			md_proc.emitter.decorator.headlines.clear
		end
	end
end

redef class WikiSection

	# The index page for this section.
	#
	# If no file `index.md` exists for this section,
	# a summary is generated using contained articles.
	var index: WikiArticle is lazy do
		for child in children.values do
			if child isa WikiArticle and child.is_index then return child
		end
		return new WikiSectionIndex(wiki, "index", self)
	end

	redef fun dir_href do return href
end

redef class WikiArticle

	# Headlines ids and titles.
	var headlines = new ArrayMap[String, HeadLine]

	# Is `self` an index page?
	#
	# Checks if `self.name == "index"`.
	fun is_index: Bool do return name == "index"

	redef fun href do
		var parent = self.parent
		if parent == null then
			return "{name}.html"
		else
			return parent.href.join_path("{name}.html")
		end
	end

	redef fun render do
		super
		if not is_dirty and not wiki.force_render or not has_source then return
		content = md_proc.process(md.as(not null))
		headlines.add_all(md_proc.emitter.decorator.headlines)
	end
end

# A `WikiArticle` that contains the section index tree.
class WikiSectionIndex
	super WikiArticle

	# The section described by `self`.
	var section: WikiSection

	redef fun title do return section.title

	redef fun href do return section.href

	redef fun dir_href do return section.dir_href
end

# A MarkdownProcessor able to parse wiki links.
class NitiwikiMdProcessor
	super MarkdownProcessor

	# Wiki used to resolve links.
	var wiki: Nitiwiki

	# Article parsed by `self`.
	#
	# Used to contextualize links.
	var context: WikiEntry

	init do
		emitter = new MarkdownEmitter(self)
		emitter.decorator = new NitiwikiDecorator(wiki, context)
	end
end

# The decorator associated to `MarkdownProcessor`.
class NitiwikiDecorator
	super HTMLDecorator

	# Wiki used to resolve links.
	var wiki: Nitiwiki

	# Article used to contextualize links.
	var context: WikiEntry

	redef fun add_wikilink(v, token) do
		var wiki = v.processor.as(NitiwikiMdProcessor).wiki
		var target: nullable WikiEntry = null
		var anchor: nullable String = null
		var link = token.link
		if link == null then return
		var name = token.name
		v.add "<a "
		if not link.has_prefix("http://") and not link.has_prefix("https://") then
			# Extract commands from the link.
			var command = null
			var command_split = link.split_once_on(":")
			if command_split.length > 1 then
				command = command_split[0].trim
				link = command_split[1].trim
			end

			if link.has("#") then
				var parts = link.split_with("#")
				link = parts.first
				anchor = parts.subarray(1, parts.length - 1).join("#")
			end
			if link.has("/") then
				target = wiki.lookup_entry_by_path(context, link.to_s)
			else
				target = wiki.lookup_entry_by_name(context, link.to_s)
				if target == null then
					target = wiki.lookup_entry_by_title(context, link.to_s)
				end
			end
			if target != null then
				if name == null then name = target.title
				link = target.href_from(context)

				if command == "trail" then
					if target isa WikiSection then target = target.index
					wiki.trails.add(context, target)
				end
			else
				wiki.message("Warning: unknown wikilink `{link}` (in {context.src_path.as(not null)})", 0)
				v.add "class=\"broken\" "
			end
		end
		v.add "href=\""
		append_value(v, link)
		if anchor != null then append_value(v, "#{anchor}")
		v.add "\""
		var comment = token.comment
		if comment != null and not comment.is_empty then
			v.add " title=\""
			append_value(v, comment)
			v.add "\""
		end
		v.add ">"
		if name == null then name = link
		v.emit_text(name)
		v.add "</a>"
	end
end