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

local M = {}

---@class ow.Git.ShowOpts
---@field split (false|"above"|"below"|"left"|"right")?  forwarded to `git.new_scratch`. Default opens a new horizontal split.

---Open a commit's `git show <ref>` output in a buffer (indented message,
---unified-diff body). For the navigable raw-object form used by the
---gitlog `<CR>` flow, see `git.object` `M.open_commit`.
---@param worktree string
---@param ref string
---@param opts ow.Git.ShowOpts?
function M.show(worktree, ref, opts)
    local split = opts and opts.split
    local sha = repo.rev_parse(worktree, ref, true) or ref
    local name = "git://" .. sha .. "//"
    -- Commit SHAs are immutable so a previously-opened buffer is still
    -- valid. Reuse it instead of refetching.
    local existing = vim.fn.bufnr(name)
    if existing ~= -1 and vim.api.nvim_buf_is_loaded(existing) then
        if split == false then
            vim.cmd.normal({ "m'", bang = true })
            vim.api.nvim_set_current_buf(existing)
        else
            vim.api.nvim_open_win(existing, true, {
                split = split or (vim.o.splitbelow and "below" or "above"),
            })
        end
        return
    end

    local stdout = util.exec({ "git", "show", ref }, { cwd = worktree })
    if not stdout then
        return
    end

    local parent = repo.rev_parse(worktree, ref .. "^", true)
    local buf, _ = git.new_scratch({ name = name, split = split })
    vim.b[buf].git_worktree = worktree
    vim.b[buf].git_ref = sha
    vim.b[buf].git_parent_ref = parent
    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
    vim.bo[buf].filetype = "git"
end

return M