--
-- 50-follow.lua
--
-- Wires the follow engine (lua/dotfiles/follow.lua): defines the followable entities and the
-- `notes://` / `nvim-help://` schemes, registers them all (in the order they are tried, first match
-- wins), then maps the gf-family keys to "open the entity under the cursor" and `]u` / `[u`
-- to cycle between entities.
--
-- Keymaps:
--   `gf`                    follow the entity under the cursor in the current window
--   `<C-w>f` / `<C-w><C-f>` ... in a split
--   `<C-w>gf`               ... in a new tab
--   `]u` / `[u`             go to the next / previous followable entity
--

-- `notes_dir` may be nil ($NOTES_DIR unset); only the wiki-link entity and the `notes://` scheme
-- need it, so the rest of the engine (markdown links, URLs, <cfile>, `nvim-help://`) wires up
-- regardless.
local notes_dir = require("dotfiles.notes").dir

local df = require("dotfiles.follow")

----------------------------------------------------------------------------------------------------
-- Wiki-links --------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------

-- All `[[wiki-link]]` matches in the buffer (markdown only), targeting the inner text.
local function wikilink_matches()
	if vim.bo.filetype ~= "markdown" then
		return {}
	end
	local out = {}
	for i, line in ipairs(vim.api.nvim_buf_get_lines(0, 0, -1, false)) do
		local init = 1
		while true do
			local s, e, inner = line:find("%[%[(.-)%]%]", init)
			if s == nil then
				break
			end
			out[#out + 1] = { from = { i, s - 1 }, to = { i, e }, target = inner }
			init = e + 1
		end
	end
	return out
end

-- Follow a `[[note]]` / `[[note#Heading]]` / `[[dir/]]` wiki-link relative to the notes dir,
-- creating parent directories (and the note itself on save) as needed.
local function open_wikilink(edit_cmd, inner)
	local name, heading = inner:match("^(.-)#(.*)$")
	if name == nil then
		name = inner
	end
	local target = notes_dir .. "/" .. name
	if name:sub(-1) == "/" then -- directory link: create and open it
		vim.fn.mkdir(target, "p")
		vim.cmd(edit_cmd .. " " .. vim.fn.fnameescape(target))
		return
	end
	if not name:match("%.%w+$") then -- default to a Markdown note
		target = target .. ".md"
	end
	vim.fn.mkdir(vim.fs.dirname(target), "p")
	vim.cmd(edit_cmd .. " " .. vim.fn.fnameescape(target))
	if heading ~= nil and heading ~= "" then
		vim.fn.cursor(1, 1)
		-- `\V` matches the heading literally; `\v` brackets the heading markers.
		local pat = [[\v^#+\s+\V]] .. vim.fn.escape(heading, [[\]]) .. [[\v\s*$]]
		if vim.fn.search(pat, "cW") == 0 then
			vim.notify("No heading '" .. heading .. "' in " .. name, vim.log.levels.WARN)
		end
	end
end

----------------------------------------------------------------------------------------------------
-- Markdown links ----------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------

-- Resolve a reference link `label` to its destination by scanning the buffer for its
-- `[label]: dest` definition (case-insensitive, per CommonMark). Returns the destination, or nil
-- if undefined.
local function resolve_link_label(label)
	-- Escape Lua pattern magic chars so the label is matched literally.
	local escaped = label:gsub("[%(%)%.%%%+%-%*%?%[%]%^%$]", "%%%1")
	-- Reference labels are case-insensitive, so match each letter against either case.
	local insensitive = escaped:gsub("%a", function(c)
		return "[" .. c:upper() .. c:lower() .. "]"
	end)
	local label_pattern = "^%[" .. insensitive .. "%]: (.*)"
	for _, line in ipairs(vim.api.nvim_buf_get_lines(0, 0, -1, true)) do
		local match = line:match(label_pattern)
		if match ~= nil then
			return match
		end
	end
	return nil
end

-- The Markdown link under the cursor (open-only), targeting its destination. Resolves reference
-- labels to their destination. Returns silently when the cursor is not on a link.
local function markdown_link_matches()
	if vim.o.filetype ~= "markdown" or vim.treesitter.get_parser(0) == nil then
		return {}
	end
	-- `ignore_injections = false` because `link_destination`/`link_label` are injected by
	-- markdown_inline.
	local node = vim.treesitter.get_node({ ignore_injections = false })
	if node == nil then
		return {}
	end
	local function is_link(type)
		return type == "full_reference_link" or type == "inline_link" or type == "shortcut_link"
	end
	local link_node
	if is_link(node:type()) then
		link_node = node
	elseif node:parent() ~= nil and is_link(node:parent():type()) then
		link_node = node:parent()
	end
	if link_node == nil then
		return {}
	end
	local dest
	for child in link_node:iter_children() do
		local text = vim.treesitter.get_node_text(child, 0)
		if child:type() == "link_destination" then
			dest = text
			break
		elseif
			child:type() == "link_label"
			or (link_node:type() == "shortcut_link" and child:type() == "link_text")
		then
			-- shortcut_link text doesn't include the `[]` unlike link_label
			if link_node:type() ~= "shortcut_link" then
				text = text:sub(2, -2)
			end
			dest = resolve_link_label(text)
			break
		end
	end
	if dest == nil then
		return {}
	end
	-- Cursor-derived match: anchor `from` at the cursor so it is open-only (never a `next` stop).
	local c = vim.api.nvim_win_get_cursor(0)
	return { { from = { c[1], c[2] }, to = { c[1], c[2] + 1 }, target = dest } }
end

----------------------------------------------------------------------------------------------------
-- Autolinks ---------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------

--[[ All CommonMark autolinks `<scheme://…>` in the buffer, targeting the inner URL with the angle
brackets stripped. Registered before the bare-URL entity so a bracketed link wins: the looser URL
scan would otherwise swallow the closing `>` and trailing punctuation into the target. The match
spans the brackets so the cursor follows from `<` through `>`. `open_target` percent-decodes the
URI, so the inner text may be percent-encoded (e.g. `<nvim-help://%27statusline%27>`). ]]
local function autolink_matches()
	local out = {}
	for i, line in ipairs(vim.api.nvim_buf_get_lines(0, 0, -1, false)) do
		local init = 1
		while true do
			local s, e, inner = line:find("<(%a[%w+.-]*://[^>%s]*)>", init)
			if s == nil then
				break
			end
			out[#out + 1] = { from = { i, s - 1 }, to = { i, e }, target = inner }
			init = e + 1
		end
	end
	return out
end

----------------------------------------------------------------------------------------------------
-- URLs --------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------

-- All `scheme://…` matches in the buffer.
local function url_matches()
	local out = {}
	for i, line in ipairs(vim.api.nvim_buf_get_lines(0, 0, -1, false)) do
		local init = 1
		while true do
			local s, e = line:find("%a[%w+.-]*://%S+", init)
			if s == nil then
				break
			end
			-- A `<scheme://…>` autolink is matched by the autolink entity; skip it here.
			local is_autolink = s > 1
				and line:sub(s - 1, s - 1) == "<"
				and line:find("^[^>%s]*>", s) ~= nil
			if not is_autolink then
				out[#out + 1] = { from = { i, s - 1 }, to = { i, e }, target = line:sub(s, e) }
			end
			init = e + 1
		end
	end
	return out
end

----------------------------------------------------------------------------------------------------
-- <cfile> fallback --------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------

-- A single open-only match at the cursor when there is a `<cfile>` under it.
local function cfile_matches()
	if vim.fn.expand("<cfile>") == "" then
		return {}
	end
	local c = vim.api.nvim_win_get_cursor(0)
	return { { from = { c[1], c[2] }, to = { c[1], c[2] + 1 }, target = true } }
end

-- Fall back to Vim's built-in gf-family (so 'path', 'suffixesadd', … apply); `feedkeys` with `n`
-- bypasses our own mappings to avoid recursion.
local builtin_gf = {
	edit = vim.keycode("gf"),
	split = vim.keycode("<C-w>f"),
	tabedit = vim.keycode("<C-w>gf"),
}
local function open_cfile(edit_cmd, _)
	vim.api.nvim_feedkeys(builtin_gf[edit_cmd], "nx", false)
end

----------------------------------------------------------------------------------------------------
-- Schemes -----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------

-- `notes://<path>` resolves to `<path>` relative to the notes dir.
local notes_scheme = {
	resolve = function(uri)
		return notes_dir .. "/" .. uri
	end,
}

-- `nvim-help://<tag>` — open Neovim help for <tag> in a scratch, read-only buffer.
local nvim_help_scheme = {
	resolve = function(uri)
		local tagfiles = {}
		for _, path in pairs(vim.opt.runtimepath:get()) do
			tagfiles[#tagfiles + 1] = path .. "/doc/tags"
		end
		vim.opt_local.tags = tagfiles
		local matches = vim.fn.taglist(uri)
		if #matches == 0 then
			return nil, "No help page found for nvim-help://" .. uri
		end
		return matches[1].filename
	end,
	after = function()
		vim.opt_local.bufhidden = "wipe"
		vim.opt_local.buftype = "nofile"
		vim.opt_local.swapfile = false
		vim.opt_local.readonly = true
	end,
}

----------------------------------------------------------------------------------------------------
-- Registration ------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------

-- Entities are tried in registration order, first match wins; `<cfile>` registers last so `gf`
-- falls back to Vim's built-in behavior. The wiki-link entity and `notes://` scheme need
-- $NOTES_DIR.
if notes_dir ~= nil then
	df.register("wikilink", wikilink_matches, open_wikilink)
	df.register_scheme("notes", notes_scheme)
else
	vim.notify(
		"50-follow.lua: NOTES_DIR is not set, wiki-link following disabled",
		vim.log.levels.WARN
	)
end
df.register("markdown-link", markdown_link_matches, df.open)
df.register("autolink", autolink_matches, df.open)
df.register("url", url_matches, df.open)
df.register("cfile", cfile_matches, open_cfile)
df.register_scheme("nvim-help", nvim_help_scheme)

----------------------------------------------------------------------------------------------------
-- Keymaps -----------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------

local function opener(edit_cmd)
	return function()
		df.open(edit_cmd)
	end
end

vim.keymap.set({ "n", "x" }, "gf", opener("edit"), { desc = "Follow entity under cursor" })
vim.keymap.set({ "n", "x" }, "<C-w>f", opener("split"), { desc = "Follow entity in a split" })
vim.keymap.set({ "n", "x" }, "<C-w><C-f>", opener("split"), { desc = "Follow entity in a split" })
vim.keymap.set({ "n", "x" }, "<C-w>gf", opener("tabedit"), { desc = "Follow entity in a new tab" })

vim.keymap.set("n", "]u", function()
	df.next(false)
end, { desc = "Go to next followable entity" })
vim.keymap.set("n", "[u", function()
	df.next(true)
end, { desc = "Go to previous followable entity" })