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

local M = {}

local LOG_FORMAT = "%h %ad {%an}%d %s"
local DEFAULT_MAX_COUNT = 1000
local URI_PREFIX = "gitlog://"

---@param worktree string
---@param max_count integer
---@return string?
local function fetch(worktree, max_count)
    local cmd = {
        "git",
        "log",
        "--graph",
        "--all",
        "--decorate",
        "--date=short",
        "--format=format:" .. LOG_FORMAT,
    }
    if max_count > 0 then
        table.insert(cmd, "--max-count=" .. max_count)
    end
    return util.exec(cmd, { cwd = worktree })
end

---@param buf integer
local function populate(buf)
    local worktree = vim.b[buf].git_worktree
    local max_count = vim.b[buf].git_log_max_count or DEFAULT_MAX_COUNT
    local stdout = fetch(worktree, max_count)
    if not stdout then
        return
    end
    vim.bo[buf].modifiable = true
    vim.api.nvim_buf_set_lines(buf, 0, -1, false, util.split_lines(stdout))
    vim.bo[buf].modifiable = false
    vim.bo[buf].modified = false
end

---BufReadCmd handler for `gitlog://<worktree>` URIs.
---@param buf integer
function M.read_uri(buf)
    local name = vim.api.nvim_buf_get_name(buf)
    local worktree = name:sub(#URI_PREFIX + 1)
    if worktree == "" then
        return
    end

    vim.b[buf].git_worktree = worktree
    vim.bo[buf].swapfile = false
    vim.bo[buf].bufhidden = "hide"
    vim.bo[buf].buftype = "nofile"
    -- Skip the assignment when ft is already set so re-runs don't
    -- re-fire `FileType` autocmds (ftplugin reload, treesitter attach).
    if vim.bo[buf].filetype ~= "gitlog" then
        vim.bo[buf].filetype = "gitlog"
    end

    populate(buf)
end

---@class ow.Git.LogOpts
---@field max_count integer?  cap on commits to show. Nil uses the default, <= 0 means "all"

---@param opts ow.Git.LogOpts?
function M.open(opts)
    opts = opts or {}
    local _, worktree = repo.resolve_cwd()
    if not worktree then
        util.warning("not in a git repository")
        return
    end

    local buf = vim.fn.bufadd(URI_PREFIX .. worktree)
    vim.b[buf].git_worktree = worktree
    vim.b[buf].git_log_max_count = opts.max_count or DEFAULT_MAX_COUNT
    local was_loaded = vim.api.nvim_buf_is_loaded(buf)

    local win = vim.fn.bufwinid(buf)
    if win == -1 then
        util.place_buf(buf, nil)
    else
        vim.api.nvim_set_current_win(win)
    end

    -- `place_buf` triggers `bufload` -> `read_uri` for a fresh buffer.
    -- An already-loaded buffer needs an explicit refresh.
    if was_loaded then
        populate(buf)
    end
end

return M