-- Minimal sticky context header. Replaces nvim-treesitter-context.
-- Shows the first line of the enclosing function/class pinned to the
-- top of the window when that line has scrolled offscreen above.
--
-- One level of context only (innermost enclosing). Extend CONTEXT_TYPES
-- to support more languages or richer node kinds.
--
-- Toggle:
--   <leader>th  hide
--   <leader>tu  unhide

local M = { enabled = true }
local ctx_buf, ctx_win

local CONTEXT_TYPES = {
    -- C / PHP
    function_definition = true,
    method_declaration = true,
    class_declaration = true,
    -- Lua
    function_declaration = true,
    -- Rust
    function_item = true,
    impl_item = true,
    trait_item = true,
    -- Go (function_declaration shared)
    -- JS
    method_definition = true,
    arrow_function = true,
    -- Zig
    fn_proto = true,
    -- Nix
    function_expression = true,
}

local function close_ctx()
    if ctx_win and vim.api.nvim_win_is_valid(ctx_win) then
        vim.api.nvim_win_close(ctx_win, true)
    end
    ctx_win = nil
end

local function update_ctx()
    if not M.enabled then close_ctx() return end

    local bufnr = vim.api.nvim_get_current_buf()
    local node = vim.treesitter.get_node()
    if not node then close_ctx() return end

    while node and not CONTEXT_TYPES[node:type()] do
        node = node:parent()
    end
    if not node then close_ctx() return end

    local sr = node:start()
    local top_visible = vim.fn.line("w0") - 1
    if sr >= top_visible then close_ctx() return end

    local lines = vim.api.nvim_buf_get_lines(bufnr, sr, sr + 1, false)
    if #lines == 0 then close_ctx() return end

    if not ctx_buf or not vim.api.nvim_buf_is_valid(ctx_buf) then
        ctx_buf = vim.api.nvim_create_buf(false, true)
        vim.bo[ctx_buf].buftype = "nofile"
    end
    vim.api.nvim_buf_set_lines(ctx_buf, 0, -1, false, lines)
    vim.bo[ctx_buf].filetype = vim.bo[bufnr].filetype

    local config = {
        relative = "win",
        win = vim.api.nvim_get_current_win(),
        row = 0,
        col = 0,
        width = vim.api.nvim_win_get_width(0),
        height = 1,
        focusable = false,
        style = "minimal",
        zindex = 20,
    }
    if ctx_win and vim.api.nvim_win_is_valid(ctx_win) then
        vim.api.nvim_win_set_config(ctx_win, config)
    else
        ctx_win = vim.api.nvim_open_win(ctx_buf, false, config)
        vim.wo[ctx_win].winhighlight = "Normal:TonyContext,NormalFloat:TonyContext"
    end
end

vim.api.nvim_set_hl(0, "TonyContext", { link = "NormalFloat", default = true })

local group = vim.api.nvim_create_augroup("TonyContext", { clear = true })
vim.api.nvim_create_autocmd({ "CursorMoved", "CursorMovedI", "WinScrolled", "BufEnter" }, {
    group = group,
    callback = update_ctx,
})
vim.api.nvim_create_autocmd({ "BufLeave", "WinLeave" }, {
    group = group,
    callback = close_ctx,
})

vim.keymap.set("n", "<leader>th", function()
    M.enabled = false
    close_ctx()
end, { desc = "Hide context header" })

vim.keymap.set("n", "<leader>tu", function()
    M.enabled = true
    update_ctx()
end, { desc = "Unhide context header" })

return M