--!strict
local fs = require("@lune/fs")
local net = require("@lune/net")
local stdio = require("@lune/stdio")

local progress_bar = require("./util/progress")
local result = require("./util/result")

--- Fetches the given file raw from the jecs github
local function fetch_raw(file: string): result.Identity<string>
    local res = net.request(`https://raw.githubusercontent.com/Ukendio/jecs/refs/heads/main/{file}`)
    if not res.ok then
        return result(false, `Not ok: {res.statusMessage} @ {res.statusCode}`)
    end
    return result(true, res.body)
end

local function save_if_diff(filepath: string, contents: string): result.Identity<nil>
    if not fs.metadata(filepath).exists then
        fs.writeFile(filepath, contents)
        return result(true, nil)
    end

    local existing = fs.readFile(filepath)
    if existing == contents then
        return result(false, "Contents are the same.")
    end

    fs.writeFile(filepath, contents)
    return result(true, nil)
end

local function round_to(n: number, places: number)
    local x = 10 ^ (places or 0)
    return math.round(n * x) / x
end

--- Synchronizes the required files from the jecs main branch.
local function sync(to: string): result.Identity<boolean>
    local begin = os.clock()

    local progress = progress_bar
        .new()
        :withStage("init", "Initializing")
        :withStage("fetch", "Fetching latest files")
        :withStage("save", "Saving files")
    progress:start()

    if not fs.metadata(to).exists then
        fs.writeDir(to)
    end

    progress:nextStage()

    local includes = {
        "jecs.luau",
        "README.md",
        "CHANGELOG.md",
        "LICENSE",
        ".luaurc",
        "default.project.json",
    }

    local sources = {}

    for _, file in includes do
        local contents = fetch_raw(file)
        if not contents.ok then
            progress:stop()
            stdio.ewrite(`🔥 Couldn't get the latest source for {file}:\n{contents.err}\n`)
            return result(false, `Couldn't get the latest source for {file}.`)
        end

        sources[file] = contents.val
    end

    progress:nextStage()

    local sources_modified = {}
    local any_changed = false
    for file, contents in sources do
        local res = save_if_diff(`{to}/{file}`, contents)
        if res.ok then
            any_changed = true
            table.insert(sources_modified, file)
        end
    end

    if not any_changed then
        progress:stop()
        local took = round_to((os.clock() - begin) * 1_000, 2)
        print(
            `🕛 Finished synchronizing, no changes since latest source {stdio.style("dim")}(took {took}ms){stdio.style(
                "reset"
            )}`
        )
        return result(true, false)
    end

    progress:stop()

    local took = round_to((os.clock() - begin) * 1_000, 2)
    print(`🪨 Finished synchronizing {stdio.style("dim")}(took {took}ms){stdio.style("reset")}`)
    print(`Changed files:`)
    print(sources_modified)

    return result(true, true)
end

return sync