-- furt-lua/src/main.lua
-- Pure Lua HTTP-Server for Furt API-Gateway
-- Dragons@Work Digital Sovereignty Project

local socket = require("socket")
local cjson = require("cjson")

-- Load configuration
local config = require("config.server")

-- HTTP-Server Module
local FurtServer = {}

function FurtServer:new()
    local instance = {
        server = nil,
        port = config.port or 8080,
        host = config.host or "127.0.0.1",
        routes = {}
    }
    setmetatable(instance, self)
    self.__index = self
    return instance
end

-- Add route handler
function FurtServer:add_route(method, path, handler)
    if not self.routes[method] then
        self.routes[method] = {}
    end
    self.routes[method][path] = handler
end

-- Parse HTTP request
function FurtServer:parse_request(client)
    local request_line = client:receive()
    if not request_line then
        return nil
    end
    
    -- Parse request line: "POST /v1/mail/send HTTP/1.1"
    local method, path, protocol = request_line:match("(%w+) (%S+) (%S+)")
    if not method then
        return nil
    end
    
    -- Parse headers
    local headers = {}
    local content_length = 0
    
    while true do
        local line = client:receive()
        if not line or line == "" then
            break
        end
        
        local key, value = line:match("([^:]+): (.+)")
        if key and value then
            headers[key:lower()] = value
            if key:lower() == "content-length" then
                content_length = tonumber(value) or 0
            end
        end
    end
    
    -- Parse body
    local body = ""
    if content_length > 0 then
        body = client:receive(content_length)
    end
    
    return {
        method = method,
        path = path,
        protocol = protocol,
        headers = headers,
        body = body,
        content_length = content_length
    }
end

-- Add CORS headers with configurable origins
function FurtServer:add_cors_headers(request)
    local allowed_origins = config.cors and config.cors.allowed_origins or {
        "http://localhost:1313",
        "http://127.0.0.1:1313",
        "https://dragons-at-work.de",
        "https://www.dragons-at-work.de"
    }
    
    -- Check if request has Origin header
    local origin = request and request.headers and request.headers.origin
    local cors_origin = "*"  -- Default fallback
    
    -- If origin is provided and in allowed list, use it
    if origin then
        for _, allowed in ipairs(allowed_origins) do
            if origin == allowed then
                cors_origin = origin
                break
            end
        end
    end
    
    return {
        ["Access-Control-Allow-Origin"] = cors_origin,
        ["Access-Control-Allow-Methods"] = "GET, POST, PUT, DELETE, OPTIONS",
        ["Access-Control-Allow-Headers"] = "Content-Type, X-API-Key, Authorization, Accept",
        ["Access-Control-Max-Age"] = "86400",
        ["Access-Control-Allow-Credentials"] = "false"
    }
end

-- Create HTTP response
function FurtServer:create_response(status, data, content_type, additional_headers, request)
    content_type = content_type or "application/json"
    local body = ""
    
    if type(data) == "table" then
        body = cjson.encode(data)
    else
        body = tostring(data or "")
    end
    
    -- Start with CORS headers
    local headers = self:add_cors_headers(request)
    
    -- Add standard headers
    headers["Content-Type"] = content_type
    headers["Content-Length"] = tostring(#body)
    headers["Connection"] = "close"
    headers["Server"] = "Furt-Lua/1.0"
    
    -- Add additional headers if provided
    if additional_headers then
        for key, value in pairs(additional_headers) do
            headers[key] = value
        end
    end
    
    -- Build response
    local response = string.format("HTTP/1.1 %d %s\r\n", status, self:get_status_text(status))
    
    for key, value in pairs(headers) do
        response = response .. key .. ": " .. value .. "\r\n"
    end
    
    response = response .. "\r\n" .. body
    
    return response
end

-- Get HTTP status text
function FurtServer:get_status_text(status)
    local status_texts = {
        [200] = "OK",
        [204] = "No Content",
        [400] = "Bad Request",
        [404] = "Not Found",
        [405] = "Method Not Allowed",
        [500] = "Internal Server Error"
    }
    return status_texts[status] or "Unknown"
end

-- Handle client request
function FurtServer:handle_client(client)
    local request = self:parse_request(client)
    if not request then
        local response = self:create_response(400, {error = "Invalid request"}, nil, nil, nil)
        client:send(response)
        return
    end
    
    print(string.format("[%s] %s %s", os.date("%Y-%m-%d %H:%M:%S"), 
          request.method, request.path))
    
    -- Handle OPTIONS preflight requests (CORS)
    if request.method == "OPTIONS" then
        local response = self:create_response(204, "", "text/plain", nil, request)
        client:send(response)
        return
    end
    
    -- Route handling
    local handler = nil
    if self.routes[request.method] and self.routes[request.method][request.path] then
        handler = self.routes[request.method][request.path]
    end
    
    if handler then
        local success, result = pcall(handler, request)
        if success then
            client:send(result)
        else
            print("Handler error: " .. tostring(result))
            local error_response = self:create_response(500, {error = "Internal server error"}, nil, nil, request)
            client:send(error_response)
        end
    else
        print("Route not found: " .. request.method .. " " .. request.path)
        local response = self:create_response(404, {error = "Route not found", method = request.method, path = request.path}, nil, nil, request)
        client:send(response)
    end
end

-- Start HTTP server
function FurtServer:start()
    self.server = socket.bind(self.host, self.port)
    if not self.server then
        error("Failed to bind to " .. self.host .. ":" .. self.port)
    end
    
    print(string.format("Furt HTTP-Server started on %s:%d", self.host, self.port))
    print("CORS enabled for all origins")
    print("Press Ctrl+C to stop")
    
    while true do
        local client = self.server:accept()
        if client then
            client:settimeout(10) -- 10 second timeout
            self:handle_client(client)
            client:close()
        end
    end
end

-- Initialize server and routes
local server = FurtServer:new()

-- Health check route
server:add_route("GET", "/health", function(request)
    local response_data = {
        status = "healthy",
        service = "furt-lua",
        version = "1.0.0",
        timestamp = os.time(),
        smtp_configured = config.mail and config.mail.username ~= nil
    }
    return server:create_response(200, response_data, nil, nil, request)
end)

-- Test route for development
server:add_route("POST", "/test", function(request)
    local response_data = {
        message = "Test endpoint working",
        received_data = request.body,
        headers_count = 0
    }
    
    -- Count headers
    for _ in pairs(request.headers) do
        response_data.headers_count = response_data.headers_count + 1
    end
    
    return server:create_response(200, response_data, nil, nil, request)
end)

-- Mail service route (placeholder for Week 1)
server:add_route("POST", "/v1/mail/send", function(request)
    print("Mail endpoint called - Method: " .. request.method .. ", Path: " .. request.path)
    
    -- Basic validation
    if not request.body or request.body == "" then
        return server:create_response(400, {error = "No request body"}, nil, nil, request)
    end
    
    -- Try to parse JSON
    local success, data = pcall(cjson.decode, request.body)
    if not success then
        return server:create_response(400, {error = "Invalid JSON", body = request.body}, nil, nil, request)
    end
    
    -- Basic field validation
    if not data.name or not data.email or not data.message then
        return server:create_response(400, {
            error = "Missing required fields",
            required = {"name", "email", "message"},
            received = data
        }, nil, nil, request)
    end
    
    -- Send email via SMTP
    local SMTP = require("src.smtp")
    local smtp_client = SMTP:new(config.mail)

    local request_id = os.time() .. "-" .. math.random(1000, 9999)
    local subject = data.subject or "Contact Form Message"
    local email_content = string.format("From: %s <%s>\nSubject: %s\n\n%s", 
        data.name, data.email, subject, data.message)

    local success, result = smtp_client:send_email(
        config.mail.to_address, subject, email_content, data.name)

    if success then
        return server:create_response(200, {
            success = true, 
            message = "Mail sent successfully", 
            request_id = request_id
        }, nil, nil, request)
    else
        print("SMTP Error: " .. tostring(result))
        return server:create_response(500, {
            success = false, 
            error = "Failed to send email: " .. tostring(result), 
            request_id = request_id
        }, nil, nil, request)
    end

end)

-- Start server
server:start()