nvim-config/lua/plugins/oil.lua

-- Track the last focused code window (not oil, not terminal)
_G.last_code_win = nil

vim.api.nvim_create_autocmd("WinEnter", {
    group = vim.api.nvim_create_augroup("track_code_win", { clear = true }),
    callback = function()
        local buf = vim.api.nvim_get_current_buf()
        local ft = vim.bo[buf].filetype
        local bt = vim.bo[buf].buftype
        if ft ~= "oil" and bt ~= "terminal" then
            _G.last_code_win = vim.api.nvim_get_current_win()
        end
    end,
})

require("oil").setup({
    watch_for_changes = true,
    keymaps = {
        ["<CR>"] = false, -- disable default, we override below
        ["<C-t>"] = false, -- don't override global <C-t> (popup terminal)
    },
})

-- Override <CR> in oil buffers to open in last code window
vim.api.nvim_create_autocmd("FileType", {
    group = vim.api.nvim_create_augroup("oil_open_in_code", { clear = true }),
    pattern = "oil",
    callback = function(ev)
        -- Go up a directory with backspace or -
        vim.keymap.set("n", "<BS>", function()
            require("oil").open(require("oil").get_current_dir() .. "..")
        end, { buffer = ev.buf, desc = "Go up directory" })

        vim.keymap.set("n", "-", function()
            require("oil").open(require("oil").get_current_dir() .. "..")
        end, { buffer = ev.buf, desc = "Go up directory" })

        -- Delete file under cursor
        vim.keymap.set("n", "<leader>d", function()
            local oil = require("oil")
            local entry = oil.get_cursor_entry()
            if not entry then return end
            local dir = oil.get_current_dir()
            if not dir then return end
            local path = dir .. entry.name
            vim.ui.input({ prompt = "Delete " .. entry.name .. "? (y/n): " }, function(input)
                if input == "y" then
                    vim.fn.delete(path, entry.type == "directory" and "rf" or "")
                    oil.discard_all_changes()
                end
            end)
        end, { buffer = ev.buf, desc = "Delete file/dir" })

        -- Open file in code window, then auto-focus back to code
        vim.keymap.set("n", "<CR>", function()
            local oil = require("oil")
            local entry = oil.get_cursor_entry()
            if not entry then return end

            -- Directories: navigate normally in oil
            if entry.type == "directory" then
                oil.select()
                return
            end

            local dir = oil.get_current_dir()
            if not dir then return end
            local filepath = dir .. entry.name
            local target_win = nil

            -- Try last focused code window
            if _G.last_code_win and vim.api.nvim_win_is_valid(_G.last_code_win) then
                local buf = vim.api.nvim_win_get_buf(_G.last_code_win)
                if vim.bo[buf].filetype ~= "oil" and vim.bo[buf].buftype ~= "terminal" then
                    target_win = _G.last_code_win
                end
            end

            -- Fallback: find any non-oil, non-terminal window
            if not target_win then
                local cur_win = vim.api.nvim_get_current_win()
                for _, win in ipairs(vim.api.nvim_tabpage_list_wins(0)) do
                    if win ~= cur_win and vim.api.nvim_win_get_config(win).relative == "" then
                        local buf = vim.api.nvim_win_get_buf(win)
                        if vim.bo[buf].filetype ~= "oil" and vim.bo[buf].buftype ~= "terminal" then
                            target_win = win
                            break
                        end
                    end
                end
            end

            if target_win then
                vim.api.nvim_set_current_win(target_win)
                -- Remember blank buffer to clean up after opening
                local old_buf = vim.api.nvim_get_current_buf()
                local is_blank = vim.api.nvim_buf_get_name(old_buf) == ""
                    and not vim.bo[old_buf].modified
                    and vim.api.nvim_buf_line_count(old_buf) <= 1
                    and vim.api.nvim_buf_get_lines(old_buf, 0, 1, false)[1] == ""
                vim.cmd.edit(vim.fn.fnameescape(filepath))
                if is_blank and old_buf ~= vim.api.nvim_get_current_buf() then
                    vim.api.nvim_buf_delete(old_buf, { force = true })
                end
            else
                -- No code window exists: create a split to the right
                vim.cmd("rightbelow vsplit " .. vim.fn.fnameescape(filepath))
            end
        end, { buffer = ev.buf, desc = "Open file in code window" })
    end,
})

-- Toggle file tree on the left with <leader>e
_G.oil_tree_win = nil

local function open_tree()
    vim.cmd("topleft vsplit | vertical resize 30")
    _G.oil_tree_win = vim.api.nvim_get_current_win()
    require("oil").open()
end

vim.keymap.set("n", "<leader>e", function()
    if _G.oil_tree_win and vim.api.nvim_win_is_valid(_G.oil_tree_win) then
        vim.api.nvim_win_close(_G.oil_tree_win, true)
        _G.oil_tree_win = nil
    else
        open_tree()
    end
end, { desc = "Toggle file tree" })

-- Open file tree on startup (deferred so oil is fully loaded)
vim.api.nvim_create_autocmd("VimEnter", {
    group = vim.api.nvim_create_augroup("oil_startup", { clear = true }),
    callback = function()
        vim.schedule(function()
            open_tree()
            vim.cmd("wincmd l")
        end)
    end,
})

-- Keep oil tree pinned at 30 columns after layout changes
vim.api.nvim_create_autocmd("WinResized", {
    group = vim.api.nvim_create_augroup("oil_pin_width", { clear = true }),
    callback = function()
        if _G.oil_tree_win and vim.api.nvim_win_is_valid(_G.oil_tree_win) then
            vim.api.nvim_win_set_width(_G.oil_tree_win, 30)
        end
    end,
})