nvim/lua/git/watcher.lua

local repo = require("git.repo")
local status = require("git.status")
local util = require("git.util")

local M = {}

---@class ow.Git.Repo
---@field gitdir string
---@field worktree string
---@field buffers table<integer, true>
---@field watcher? uv.uv_fs_event_t
---@field refresh fun(self: ow.Git.Repo)
---@field refresh_handle ow.Git.Util.DebounceHandle
local Repo = {}
Repo.__index = Repo

function Repo:start_watcher()
    local watcher = assert(vim.uv.new_fs_event())
    assert(watcher:start(self.gitdir, {}, function(err, filename)
        if err or (filename ~= "index" and filename ~= "HEAD") then
            return
        end
        self:refresh()
    end))
    self.watcher = watcher
end

function Repo:stop_watcher()
    -- Stop the libuv watcher first so no further fs-events can trigger
    -- self:refresh(). Tearing down the debounce handle first leaves a
    -- window where an in-flight watcher callback hits a closed timer.
    if self.watcher then
        self.watcher:stop()
        self.watcher:close()
        self.watcher = nil
    end
    self.refresh_handle.close()
end

---@param buf integer
function Repo:add_buffer(buf)
    self.buffers[buf] = true
end

---@param buf integer
function Repo:remove_buffer(buf)
    self.buffers[buf] = nil
end

---@return boolean
function Repo:has_buffers()
    return next(self.buffers) ~= nil
end

---@param r ow.Git.Repo
local function do_refresh(r)
    vim.system(
        {
            "git",
            "-c",
            "core.quotePath=false",
            "status",
            "--porcelain=v1",
            "--branch",
        },
        { cwd = r.worktree, text = true },
        vim.schedule_wrap(function(obj)
            local statuses = {}
            if obj.code == 0 then
                for line in (obj.stdout or ""):gmatch("[^\r\n]+") do
                    if line:sub(1, 2) ~= "##" then
                        local code = line:sub(1, 2)
                        local x = code:sub(1, 1)
                        local y = code:sub(2, 2)
                        local path_part = line:sub(4)
                        if x == "R" or x == "C" or y == "R" or y == "C" then
                            local arrow = path_part:find(" -> ", 1, true)
                            if arrow then
                                path_part = path_part:sub(arrow + 4)
                            end
                        end
                        statuses[vim.fs.joinpath(r.worktree, path_part)] =
                            status.format(code)
                    end
                end
            else
                util.warning(
                    "git status failed: %s",
                    vim.trim(obj.stderr or "")
                )
            end
            local dirty = false
            for buf in pairs(r.buffers) do
                if not vim.api.nvim_buf_is_valid(buf) then
                    r.buffers[buf] = nil
                else
                    local status = statuses[vim.api.nvim_buf_get_name(buf)]
                    if vim.b[buf].git_status ~= status then
                        vim.b[buf].git_status = status
                        dirty = true
                    end
                end
            end
            if dirty then
                vim.cmd.redrawstatus({ bang = true })
            end
            vim.api.nvim_exec_autocmds("User", {
                pattern = "GitRefresh",
                data = {
                    gitdir = r.gitdir,
                    worktree = r.worktree,
                    porcelain_stdout = obj.code == 0 and obj.stdout or nil,
                },
            })
        end)
    )
end

---@param gitdir string
---@param worktree string
---@return ow.Git.Repo
function Repo.new(gitdir, worktree)
    local self = setmetatable({
        gitdir = gitdir,
        worktree = worktree,
        buffers = {},
    }, Repo)
    self.refresh, self.refresh_handle = util.debounce(do_refresh, 50)
    self:start_watcher()
    return self
end

---@type table<string, ow.Git.Repo>
local repo_by_gitdir = {}

---@type table<integer, ow.Git.Repo>
local repo_by_buf = {}

---@param buf integer
---@return ow.Git.Repo?
local function register(buf)
    local existing = repo_by_buf[buf]
    if existing then
        return existing
    end
    local path = vim.api.nvim_buf_get_name(buf)
    if path == "" then
        return nil
    end
    local gitdir, worktree = repo.resolve(path)
    if not gitdir or not worktree then
        return nil
    end
    local r = repo_by_gitdir[gitdir]
    if not r then
        r = Repo.new(gitdir, worktree)
        repo_by_gitdir[gitdir] = r
    end
    r:add_buffer(buf)
    repo_by_buf[buf] = r
    return r
end

---@param buf integer
function M.unregister(buf)
    local r = repo_by_buf[buf]
    if not r then
        return
    end
    repo_by_buf[buf] = nil
    r:remove_buffer(buf)
    if not r:has_buffers() then
        r:stop_watcher()
        repo_by_gitdir[r.gitdir] = nil
    end
end

---@param buf integer
function M.refresh_buf(buf)
    if not vim.api.nvim_buf_is_valid(buf) or vim.bo[buf].buftype ~= "" then
        return
    end
    local r = register(buf)
    if not r then
        vim.b[buf].git_status = nil
        return
    end
    r:refresh()
end

function M.stop_all()
    for _, r in pairs(repo_by_gitdir) do
        r:stop_watcher()
    end
end

return M