--- `[[wiki-link]]` parsing and following (tech-spec §8).
---
--- The cursor grammar mirrors `heph-core`'s `extract.rs`: a span `[[target]]`
--- or `[[target|display]]`, where the resolvable name is everything left of the
--- first `|`, trimmed. Resolution goes through `node.resolve` (exact, the same
--- mapping that materializes stored `wiki` links) — never fuzzy `search`, which
--- would mis-jump.

local rpc = require("heph.rpc")
local util = require("heph.util")

local M = {}

--- The wiki target under the cursor on the current line, or nil. Scans for the
--- `[[...]]` span that contains the cursor column.
function M.target_under_cursor()
  local line = vim.api.nvim_get_current_line()
  local col = vim.api.nvim_win_get_cursor(0)[2] + 1 -- 1-based byte column
  local from = 1
  while true do
    local open_s, open_e = line:find("[[", from, true)
    if not open_s then
      return nil
    end
    local close_s, close_e = line:find("]]", open_e + 1, true)
    if not close_s then
      return nil
    end
    if col >= open_s and col <= close_e then
      local inner = line:sub(open_e + 1, close_s - 1)
      local target = inner:match("^([^|]*)") or ""
      target = target:gsub("^%s+", ""):gsub("%s+$", "")
      return (#target > 0) and target or nil
    end
    from = close_e + 1
  end
end

--- Follow the `[[link]]` under the cursor to its node, **creating** the target
--- doc if it doesn't exist yet (the zettelkasten follow-or-create gesture). The
--- newly-created doc resolves the source's previously-unresolved wiki-link, so
--- re-saving the source materializes the backlink.
function M.follow()
  local target = M.target_under_cursor()
  if not target then
    util.notify("no [[link]] under cursor", vim.log.levels.WARN)
    return
  end
  local node = rpc.call("node.resolve", { title = target })
  if not node then
    node = rpc.call("node.create", { kind = "doc", title = target, body = "" })
    util.notify("created [[" .. target .. "]]")
    -- Materialize the source's wiki-link to the new doc — it was unresolved when
    -- the source was saved, so extraction skipped it (tech-spec §5). If the
    -- source has unsaved edits, saving re-extracts and materializes it (and
    -- persists the edits); otherwise add the link directly (a no-op re-save
    -- wouldn't re-extract).
    local src = vim.api.nvim_get_current_buf()
    local src_id = vim.b[src].heph_node_id
    if src_id then
      if vim.bo[src].modified then
        pcall(require("heph.node").write, src, vim.api.nvim_buf_get_name(src))
      else
        pcall(rpc.call, "links.add", { src = src_id, dst = node.id, link_type = "wiki" })
      end
    end
  end
  require("heph.node").open(node.id)
end

--- Attach the buffer-local `<CR>` follow keymap (only on heph:// buffers).
function M.attach(buf)
  vim.keymap.set("n", "<CR>", function()
    M.follow()
  end, { buffer = buf, desc = "heph: follow [[link]]" })
end

return M