local M = {}

local CACHE_VERSION = 1
local CACHE_DIR = vim.fn.stdpath("cache") .. "/skift"

local SOURCE_FILES = {
    "lua/skift/palette.lua",
    "lua/skift/init.lua",
    "lua/skift/groups/editor.lua",
    "lua/skift/groups/syntax.lua",
    "lua/skift/groups/treesitter.lua",
    "lua/skift/groups/lsp.lua",
    "lua/skift/groups/integrations.lua",
    "lua/skift/utils/palette.lua",
}

local function function_fingerprint(fn)
    if type(fn) ~= "function" then
        return tostring(fn)
    end

    local ok, dumped = pcall(string.dump, fn)
    if ok and dumped then
        return vim.fn.sha256(dumped)
    end

    local info = debug.getinfo(fn, "S")
    if info and info.source then
        return string.format("%s:%d", info.source, info.linedefined or 0)
    end

    return tostring(fn)
end

local function source_fingerprint()
    local stamp = {}

    for _, pattern in ipairs(SOURCE_FILES) do
        local path = vim.api.nvim_get_runtime_file(pattern, false)[1]
        if path then
            local stat = vim.loop.fs_stat(path)
            stamp[#stamp + 1] = {
                file = pattern,
                mtime = stat and stat.mtime and stat.mtime.sec or 0,
                size = stat and stat.size or 0,
            }
        else
            stamp[#stamp + 1] = { file = pattern, mtime = 0, size = 0 }
        end
    end

    return stamp
end

local function cache_file(cache_key)
    return CACHE_DIR .. "/highlights-" .. cache_key .. ".json"
end

---@param config Config
function M.key(config)
    local payload = {
        version = CACHE_VERSION,
        transparent = config.transparent,
        bold = config.bold,
        italic = config.italic,
        italic_comments = config.italic_comments,
        on_colors = function_fingerprint(config.on_colors),
        on_highlights = function_fingerprint(config.on_highlights),
        sources = source_fingerprint(),
    }

    return vim.fn.sha256(vim.json.encode(payload))
end

function M.read(cache_key)
    local path = cache_file(cache_key)
    if vim.fn.filereadable(path) == 0 then
        return nil
    end

    local ok_read, lines = pcall(vim.fn.readfile, path)
    if not ok_read or not lines then
        return nil
    end

    local raw = table.concat(lines, "\n")
    local ok_decode, decoded = pcall(vim.json.decode, raw)
    if not ok_decode then
        return nil
    end

    return decoded
end

function M.write(cache_key, payload)
    vim.fn.mkdir(CACHE_DIR, "p")
    local path = cache_file(cache_key)
    local encoded = vim.json.encode(payload)
    local ok_write = pcall(vim.fn.writefile, { encoded }, path)
    return ok_write
end

function M.clear()
    vim.fn.delete(CACHE_DIR, "rf")
end

return M