// HTTP API Example
//
// A complete REST API demonstrating:
// - Route matching with path parameters
// - Response builders
// - JSON construction
//
// Run with: lux examples/http_api.lux
// Test with:
//   curl http://localhost:8080/
//   curl http://localhost:8080/users
//   curl http://localhost:8080/users/42

// ============================================================
// Response Helpers
// ============================================================

fn httpOk(body: String): { status: Int, body: String } =
    { status: 200, body: body }

fn httpCreated(body: String): { status: Int, body: String } =
    { status: 201, body: body }

fn httpNotFound(body: String): { status: Int, body: String } =
    { status: 404, body: body }

fn httpBadRequest(body: String): { status: Int, body: String } =
    { status: 400, body: body }

// ============================================================
// JSON Helpers
// ============================================================

fn jsonEscape(s: String): String =
    String.replace(String.replace(s, "\\", "\\\\"), "\"", "\\\"")

fn jsonStr(key: String, value: String): String =
    "\"" + jsonEscape(key) + "\":\"" + jsonEscape(value) + "\""

fn jsonNum(key: String, value: Int): String =
    "\"" + jsonEscape(key) + "\":" + toString(value)

fn jsonObj(content: String): String =
    "{" + content + "}"

fn jsonArr(content: String): String =
    "[" + content + "]"

fn jsonError(message: String): String =
    jsonObj(jsonStr("error", message))

// ============================================================
// Path Matching
// ============================================================

fn pathMatches(path: String, pattern: String): Bool = {
    let pathParts = String.split(path, "/")
    let patternParts = String.split(pattern, "/")
    if List.length(pathParts) != List.length(patternParts) then false
    else matchParts(pathParts, patternParts)
}

fn matchParts(pathParts: List<String>, patternParts: List<String>): Bool = {
    if List.length(pathParts) == 0 then true
    else {
        match List.head(pathParts) {
            None => true,
            Some(pathPart) => {
                match List.head(patternParts) {
                    None => true,
                    Some(patternPart) => {
                        let isMatch = if String.startsWith(patternPart, ":") then true else pathPart == patternPart
                        if isMatch then {
                            let restPath = Option.getOrElse(List.tail(pathParts), [])
                            let restPattern = Option.getOrElse(List.tail(patternParts), [])
                            matchParts(restPath, restPattern)
                        } else false
                    }
                }
            }
        }
    }
}

fn getPathSegment(path: String, index: Int): Option<String> = {
    let parts = String.split(path, "/")
    List.get(parts, index + 1)
}

// ============================================================
// Handlers
// ============================================================

fn indexHandler(): { status: Int, body: String } =
    httpOk(jsonObj(jsonStr("message", "Welcome to Lux HTTP API")))

fn healthHandler(): { status: Int, body: String } =
    httpOk(jsonObj(jsonStr("status", "healthy")))

fn listUsersHandler(): { status: Int, body: String } = {
    let user1 = jsonObj(jsonNum("id", 1) + "," + jsonStr("name", "Alice"))
    let user2 = jsonObj(jsonNum("id", 2) + "," + jsonStr("name", "Bob"))
    httpOk(jsonArr(user1 + "," + user2))
}

fn getUserHandler(path: String): { status: Int, body: String } = {
    match getPathSegment(path, 1) {
        Some(id) => {
            let body = jsonObj(jsonStr("id", id) + "," + jsonStr("name", "User " + id))
            httpOk(body)
        },
        None => httpNotFound(jsonError("User not found"))
    }
}

fn createUserHandler(body: String): { status: Int, body: String } = {
    let newUser = jsonObj(jsonNum("id", 3) + "," + jsonStr("name", "New User"))
    httpCreated(newUser)
}

// ============================================================
// Router
// ============================================================

fn router(method: String, path: String, body: String): { status: Int, body: String } = {
    if method == "GET" && path == "/" then indexHandler()
    else if method == "GET" && path == "/health" then healthHandler()
    else if method == "GET" && path == "/users" then listUsersHandler()
    else if method == "GET" && pathMatches(path, "/users/:id") then getUserHandler(path)
    else if method == "POST" && path == "/users" then createUserHandler(body)
    else httpNotFound(jsonError("Not found: " + path))
}

// ============================================================
// Server
// ============================================================

fn serveLoop(remaining: Int): Unit with {Console, HttpServer} = {
    if remaining <= 0 then {
        Console.print("Max requests reached, stopping server.")
        HttpServer.stop()
    } else {
        let req = HttpServer.accept()
        Console.print(req.method + " " + req.path)
        let resp = router(req.method, req.path, req.body)
        HttpServer.respond(resp.status, resp.body)
        serveLoop(remaining - 1)
    }
}

fn main(): Unit with {Console, HttpServer} = {
    let port = 8080
    let maxRequests = 10
    Console.print("========================================")
    Console.print("  Lux HTTP API Demo")
    Console.print("========================================")
    Console.print("")
    Console.print("Endpoints:")
    Console.print("  GET  /           - API info")
    Console.print("  GET  /health     - Health check")
    Console.print("  GET  /users      - List users")
    Console.print("  GET  /users/:id  - Get user by ID")
    Console.print("  POST /users      - Create user")
    Console.print("")
    Console.print("Try:")
    Console.print("  curl http://localhost:8080/")
    Console.print("  curl http://localhost:8080/users")
    Console.print("  curl http://localhost:8080/users/42")
    Console.print("  curl -X POST http://localhost:8080/users")
    Console.print("")
    Console.print("Starting server on port " + toString(port) + "...")
    HttpServer.listen(port)
    Console.print("Server listening!")
    serveLoop(maxRequests)
}

let output = run main() with {}