// shellApp.h — DVX Shell application lifecycle types and API
//
// The shell supports two kinds of DXE apps:
//
// 1. Callback-only apps (hasMainLoop = false):
//    appMain() is called directly in the shell's task 0. It creates
//    windows, registers event callbacks, and returns immediately. The
//    app then lives entirely through GUI callbacks driven by the shell's
//    main loop. This is simpler and cheaper (no extra stack/task) and
//    is the right choice for apps that are purely event-driven (dialogs,
//    simple tools). Lifecycle ends when the last window is closed.
//
// 2. Main-loop apps (hasMainLoop = true):
//    A dedicated cooperative task is created for the app. appMain() runs
//    in that task and can do its own polling/processing loop, calling
//    tsYield() to share CPU. This is needed for apps that have continuous
//    work (terminal emulators, games, long computations). Lifecycle ends
//    when appMain() returns or the task is killed.
//
// Both types use the same DXE interface (appDescriptor + appMain), so
// app authors choose by setting hasMainLoop in their descriptor.
#ifndef SHELL_APP_H
#define SHELL_APP_H

#include "dvxApp.h"
#include "dvxWidget.h"
#include "taskswitch.h"

#include <stdint.h>
#include <stdbool.h>

// ============================================================
// App descriptor (exported by each DXE app)
// ============================================================

#define SHELL_APP_NAME_MAX 64
// Fixed array size for app slots. A small fixed limit avoids dynamic
// allocation complexity and matches the practical limit of a DOS desktop.
// Slot 0 is reserved for the shell itself, so 31 app slots are usable.
#define SHELL_MAX_APPS     32

// Every DXE app exports a global AppDescriptorT named "appDescriptor".
// The shell reads it at load time to determine how to launch the app.

// Use in AppDescriptorT.stackSize to get the default task stack size
#define SHELL_STACK_DEFAULT 0

typedef struct {
    char    name[SHELL_APP_NAME_MAX];
    bool    hasMainLoop;
    bool    multiInstance;  // true = allow multiple instances via temp copy
    int32_t stackSize;      // SHELL_STACK_DEFAULT or explicit byte count
    int32_t priority;       // TS_PRIORITY_* or custom
} AppDescriptorT;

// ============================================================
// App context (passed to appMain)
// ============================================================

// Passed as the sole argument to appMain(). Gives the app access to
// the shell's GUI context (for creating windows, drawing, etc.) and
// its own identity. appDir is derived from the .app file path at load
// time so the app can find its own resources (icons, data files) via
// relative paths — important because the working directory is shared
// by all apps and can't be changed per-app in DOS.
typedef struct {
    AppContextT *shellCtx;  // the shell's GUI context
    int32_t      appId;     // this app's ID
    char         appDir[260]; // directory containing the .app file
} DxeAppContextT;

// ============================================================
// Per-app state
// ============================================================

// State machine:  Free -> Loaded -> Running -> Terminating -> Free
// LoadedE is transient (only during shellLoadApp before entry is called).
// TerminatingE means the app's task has exited but cleanup (window
// destruction, DXE unload) hasn't happened yet — the shell's main loop
// reaps these each frame via shellReapApps().
typedef enum {
    AppStateFreeE,          // slot available
    AppStateLoadedE,        // DXE loaded, not yet started
    AppStateRunningE,       // entry point called, active
    AppStateTerminatingE    // shutdown in progress
} AppStateE;

typedef struct {
    int32_t     appId;          // unique ID = slot index (1-based; 0 = shell)
    char        name[SHELL_APP_NAME_MAX];
    char        path[260];
    char        tempPath[260];  // temp copy path for multi-instance (empty = not a copy)
    void       *dxeHandle;      // dlopen() handle
    AppStateE   state;
    bool        hasMainLoop;
    uint32_t    mainTaskId;     // task ID if hasMainLoop, else 0
    int32_t   (*entryFn)(DxeAppContextT *);
    void      (*shutdownFn)(void);   // may be NULL
    DxeAppContextT dxeCtx;      // context passed to appMain
} ShellAppT;

// ============================================================
// Shell global state
// ============================================================

// Current app ID for resource tracking (0 = shell).
// Set before calling any app code (entry, shutdown, callbacks) so that
// wrapper functions (shellWrapCreateWindow, etc.) can stamp newly created
// resources with the correct owner. This is the mechanism that lets the
// shell know which windows belong to which app, enabling per-app cleanup
// on crash or termination. It's a global rather than a thread-local
// because cooperative multitasking means only one task runs at a time.
extern int32_t sCurrentAppId;

// ============================================================
// App lifecycle API
// ============================================================

// Initialize the app slot table
void shellAppInit(void);

// Load and start an app from a DXE file. Returns app ID (>= 1) or -1 on error.
// For callback-only apps, appMain runs synchronously and returns before
// shellLoadApp returns. For main-loop apps, a task is created and the
// app starts running on the next tsYield.
int32_t shellLoadApp(AppContextT *ctx, const char *path);

// Reap finished apps (call each frame from main loop). Returns true if
// any apps were reaped, so the caller can notify the desktop to refresh.
// For callback-only apps, termination is triggered by shellWrapDestroyWindow
// when the last window closes. For main-loop apps, termination happens
// when appMain returns (via appTaskWrapper marking AppStateTerminatingE).
bool shellReapApps(AppContextT *ctx);

// Gracefully shut down a single app — calls shutdownFn if present,
// destroys windows, kills task, closes DXE handle.
void shellReapApp(AppContextT *ctx, ShellAppT *app);

// Forcibly kill an app (Task Manager "End Task"). Skips shutdownFn —
// used when the app is hung or has crashed and cannot be trusted to
// run its own cleanup code.
void shellForceKillApp(AppContextT *ctx, ShellAppT *app);

// Terminate all running apps (shell shutdown)
void shellTerminateAllApps(AppContextT *ctx);

// Get app slot by ID (returns NULL if invalid/free)
ShellAppT *shellGetApp(int32_t appId);

// Count running apps (not counting the shell itself)
int32_t shellRunningAppCount(void);

// ============================================================
// Logging
// ============================================================

// Write a printf-style message to DVX.LOG
void shellLog(const char *fmt, ...);

// ============================================================
// DXE export table
// ============================================================

// Register the DXE symbol export table (call before any dlopen)
void shellExportInit(void);

// ============================================================
// Desktop callback
// ============================================================

// Default desktop app path
#define SHELL_DESKTOP_APP "apps/progman/progman.app"

// Register a callback for app state changes (load, reap, crash).
// The desktop app (Program Manager) calls this during appMain to receive
// notifications so it can refresh its task list / window list display.
// Only one callback is supported — the desktop is always loaded first
// and is the only consumer.
void shellRegisterDesktopUpdate(void (*updateFn)(void));

#endif // SHELL_APP_H