#!/bin/lua

--[[ Copyright (c) 2026 Alexander Hill

Permission to use, copy, modify, and/or distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE. ]]

local posix = require("posix")
local tinytoml = require("tinytoml")

local config
local config_path = "/etc/maple.toml"
local sysroot = "/"
local templates = "/usr/share/mapleconf"

local function tokenize_block(inner)
    local buffer = ""
    local escaped = false
    local quoted = false
    local tokens = {}

    for char in inner:gmatch(".") do
        if escaped then
            buffer = buffer .. char
            escaped = false

        elseif char == "\\" then
            if quoted then
                buffer = buffer .. char
            end

            escaped = true

        elseif quoted then
            buffer = buffer .. char

            if char == "\"" then
                quoted = false
                table.insert(tokens, buffer)
                buffer = ""
            end

        else
            if char:match("%s") then
                if #buffer > 0 then
                    table.insert(tokens, buffer)
                    buffer = ""
                end

            elseif char == "\"" then
                buffer = buffer .. char
                quoted = true

            else
                buffer = buffer .. char
            end
        end
    end

    if #buffer > 0 then
        table.insert(tokens, buffer)
    end

    return tokens
end

-- Symbol Reference:
-- {"if", condition, true, false} - Executes true if condition is "truthy" and false otherwise
-- {"literal", string} - Writes `string` to the target
-- {"string", string} - Format and write string to the target
-- {"value", identifier} - Returns the value of the identifier

local function tokenize_template(raw)
    local current = 0
    local last = 0
    local literal = true
    local template = {}

    while current do
        current = string.find(raw, "@", current + 1)

        if current then
            -- TODO: What happens when a line ends with a backslash? ~ahill
            if raw:sub(current - 1, current - 1) ~= "\\" then
                if literal then
                    table.insert(template, { "literal", string.sub(raw, last + 1, current - 1) })
                    literal = false

                else
                    if current - last == 1 then
                        table.insert(template, { "literal", "@" })

                    else
                        local inner = raw:sub(last + 1, current - 1)

                        if inner:sub(1, 1) ~= "-" then
                            local tokens = tokenize_block(inner)

                            print(#tokens)
                            for _, v in ipairs(tokens) do
                                print(v)
                                if v == "nil" then
                                    table.insert(template, { "literal", "" })

                                elseif v:sub(1, 1) == "\"" and v:sub(-1, -1) == "\"" then
                                    table.insert(template, { "string", v:sub(2, -2) })

                                else
                                    table.insert(template, {"value", v})
                                end
                            end

                            -- ...
                        end
                    end
                    literal = true
                end

                last = current
            end

        else
            table.insert(template, { "literal", string.sub(raw, last + 1) })
            last = current
        end
    end

    return template
end

local function render_template(source, target)
    local raw = source:read("*all")
    local result = ""
    local template = tokenize_template(raw)

    for _, v in ipairs(template) do
        if v[1] == "literal" then
            result = result .. v[2]

        elseif v[1] == "string" then
            result = result .. v[2]

        elseif v[1] == "value" then
            if config[v[2]] then
                result = result .. config[v[2]]
            else
                print("Unable to locate " .. v[2])
                return
            end

        else
            print("BUG: Symbol type " .. v[1] .. " was not recognized!")
            return
        end
    end

    target:write(result)
end

local function render_directory(stack)
    local path
    if #stack == 0 then
        path = "/"
    else
        path = "/" .. table.concat(stack, "/") .. "/"
    end

    local files = posix.dir(templates .. path)
    for _, entry in ipairs(files) do
        if not string.match(entry, "^%.+$") then
            local fullpath = path .. entry

            local stat = posix.stat(templates .. fullpath)
            if stat.type == "directory" then
                if not posix.access(sysroot .. fullpath) then
                    posix.mkdir(sysroot .. fullpath)
                end

                local newstack = {}
                -- Why does Lua lack the ability to copy tables? ~ahill
                for _, v in ipairs(stack) do
                    table.insert(newstack, v)
                end
                table.insert(newstack, entry)
                render_directory(newstack)

            elseif stat.type == "regular" then
                print("Updating " .. fullpath)

                local template = io.open(templates .. fullpath, "r")
                if template then
                    local target = io.open(sysroot .. fullpath, "w")
                    if target then
                        render_template(template, target)
                        target:close()
                    end
                    template:close()
                end

            else
                print("BUG: Directory entry type " .. stat.type .. " not recognized.")
            end
        end
    end
end

-- ENTRY POINT

for opt, optarg, optind in posix.unistd.getopt(arg, "c:hr:t:") do
    if opt == "c" then
        config_path = optarg
    elseif opt == "h" then
        -- Pardon the formatting. This should be cleaned up later. ~ahill
        print[[Usage: mapleconf [option [option ...] ]
    -c <file> - Sets the file to source configuration data from
    -h        - Displays this help message
    -r <path> - Sets the sysroot to configure
    -t <path> - Sets the path of the template directory]]
        os.exit(1)
    elseif opt == "r" then
        sysroot = optarg
    elseif opt == "t" then
        templates = optarg
    else
        print("Unknown option: " .. arg[optind - 1])
        os.exit(1)
    end
end

config = tinytoml.parse(config_path)

render_directory{}