#ifndef TERM_H
#define TERM_H

/*
 * Terminal emulator core.
 *
 * A struct term parses the bytes that a program writes and keeps the screen,
 * the history, and the modes. The application feeds bytes with term_feed()
 * and reads state with the getters below. A renderer never reads the
 * terminal directly: it copies the viewport into a struct term_snapshot and
 * paints from that copy.
 *
 * All functions take the terminal as the first argument. Functions that take
 * a const struct term do not change what it shows. Selection, history, link,
 * directory, and pointer-shape queries return owned strings; release them
 * with term_text_free().
 *
 * Threads. Any thread can call any function. Each call that reads or changes
 * a terminal enters its writer section, so calls on one terminal run one at a
 * time. A thread that waits for the section sleeps. On POSIX the section is a
 * mutex with priority inheritance where the platform has it. A snapshot
 * belongs to one thread at a time. term_free() is the last call on a terminal.
 */

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

#include "term_input.h"
#include "term_types.h"

#ifdef __cplusplus
extern "C" {
#endif

struct term;
struct term_snapshot;

/* A row holds at most this many cells. */
#define TERM_MAX_COLS 65535
/* The history limit when term_options.scrollback is 0. */
#define TERM_SCROLLBACK_DEFAULT 10000

/*
 * Colors. A term_color is either a direct color (alpha 0xFF, then RGB) or a
 * palette slot: an index 0-255, the default foreground, or the default
 * background. A slot resolves when a snapshot is painted, so a theme change
 * recolors text that is already on screen.
 */
typedef uint32_t term_color;

#define TERM_COLOR_SLOT 0x01000000u
/* The palette index of a slot; see struct term_view.palette. */
#define TERM_COLOR_SLOT_INDEX 0x1FFu
#define TERM_COLOR_FG (TERM_COLOR_SLOT | 0x100u)
#define TERM_COLOR_BG (TERM_COLOR_SLOT | 0x101u)

static inline term_color term_color_index(int n)
{
    return TERM_COLOR_SLOT | ((uint32_t)n & 0xFFu);
}

static inline term_color term_color_rgb(uint8_t r, uint8_t g, uint8_t b)
{
    return 0xFF000000u | (uint32_t)r << 16 | (uint32_t)g << 8 | b;
}

static inline bool term_color_is_slot(term_color c)
{
    return (c >> 24) == (TERM_COLOR_SLOT >> 24);
}

/* Parse an X11 or OSC color specification ("#rgb", "rgb:r/g/b", ...). */
TERM_API bool term_color_parse(const char *spec, uint32_t *argb);

/* The colors a terminal starts with. All values are ARGB. An all-zero theme
 * selects the built-in theme. */
struct term_theme {
    uint32_t fg, bg, cursor;
    uint32_t ansi[16];
};

/* Fill theme with the built-in theme. */
TERM_API void term_theme_default(struct term_theme *theme);
/* Fill theme with the high-contrast theme. */
TERM_API void term_theme_high_contrast(struct term_theme *theme);
/* Sets one palette key: foreground, background, or color0 to color15.
 * An empty value resets the key to the built-in theme. False, with no
 * change, for an unknown key or a bad color. */
TERM_API bool term_theme_set_key(struct term_theme *p, const char *key, const char *val);

enum term_cursor_style {
    TERM_CURSOR_BLOCK,
    TERM_CURSOR_UNDERLINE,
    TERM_CURSOR_BAR,
};

/* Mouse reporting modes and encodings. The values are the DEC mode numbers. */
enum term_mouse {
    TERM_MOUSE_OFF = 0,
    TERM_MOUSE_X10 = 9,
    TERM_MOUSE_NORMAL = 1000,
    TERM_MOUSE_BUTTON = 1002,
    TERM_MOUSE_ANY = 1003,
};

enum term_mouse_encoding {
    TERM_MOUSE_ENC_X10 = 0,
    TERM_MOUSE_ENC_UTF8 = 1005,
    TERM_MOUSE_ENC_SGR = 1006,
    TERM_MOUSE_ENC_URXVT = 1015,
    TERM_MOUSE_ENC_SGR_PIXELS = 1016,
};

/*
 * Callbacks. They run inside term_feed() and term_focus(), on the thread
 * that calls those functions. A callback must not call back into the
 * terminal. String arguments are valid only during the call.
 */
struct term_callbacks {
    void *ud;
    /* Bytes the terminal sends back to the program (replies to queries). */
    void (*reply)(void *ud, const char *bytes, size_t len);
    void (*title)(void *ud, const char *title);
    /*
     * OSC 52 clipboard callback.
     * selection names the target clipboard buffer(s), commonly:
     *   "c" - clipboard (system clipboard)
     *   "p" - primary selection (X11 primary)
     *   "q" - secondary selection
     *   "s" - select selection
     *   "0".."7" - cut buffers 0 to 7
     * A parameter may contain multiple targets (e.g. "cp").
     * data contains decoded bytes of length len.
     */
    void (*clipboard)(void *ud, const char *selection, const char *data, size_t len);
    void (*notify)(void *ud, const char *title, const char *body);
    void (*bell)(void *ud);
    /* Parser trace lines for debugging. NULL turns tracing off. The line has no newline. */
    void (*trace)(void *ud, const char *line);
};

/* Options for term_new(). An all-zero value is valid. */
struct term_options {
    struct term_vector2i size;  /* columns and rows; each is at least 1 */
    int scrollback;             /* history lines; 0 selects TERM_SCROLLBACK_DEFAULT */
    struct term_theme theme;
    enum term_cursor_style cursor_style;
    bool cursor_steady;         /* false: the cursor blinks */
    struct term_callbacks callbacks;
};

/* NULL when memory runs out. */
/* The Unicode version of the width tables, such as "18.0.0". A host can
 * pass it to programs as UNICODE_VERSION. */
TERM_API const char *term_unicode_version(void);

/* The length of the prefix of buf made of bytes in [0x20, hi). With hi
 * 0x7f, it finds a run of printable ASCII in UTF-8 text, so a host can
 * skip shaping for it. Any thread can call it. */
TERM_API size_t term_scan_printable_span(const char *buf, size_t len, unsigned char hi);

/* The instruction set level of the running code: "base", "avx2", "avx512",
 * or "neon". On x86-64, the first term_new() picks the highest level the CPU
 * supports. Set TERM_HEADLESS_ISA to a lower level to force it, for tests
 * and comparisons. */
TERM_API const char *term_isa(void);

TERM_API struct term *term_new(const struct term_options *opt);
TERM_API void term_free(struct term *t);

/* Hold the writer section across several calls, so that no other thread
 * changes the terminal between them. The section is a mutex, and a waiting
 * thread sleeps. Keep it short. The thread that holds it can call every
 * function, and it can enter the section again. Each term_lock() needs one
 * term_unlock(). */
TERM_API void term_lock(struct term *t);
TERM_API void term_unlock(struct term *t);

/* Change the size in cells. Returns false when memory runs out; the terminal
 * is then unchanged. The screen reflows to the new width. */
TERM_API bool term_resize(struct term *t, struct term_vector2i size);

/* Replace the theme. A different theme also drops the colors that the
 * program set with OSC; the same theme changes nothing. */
TERM_API void term_set_theme(struct term *t, const struct term_theme *theme);

/* The cursor style that DECSCUSR 0 and a reset restore. */
TERM_API void term_set_cursor_default(struct term *t, enum term_cursor_style style, bool steady);

/*
 * Bytes from the program.
 *
 * TERM_FEED_ONLCR: a line feed also returns the cursor to column 0, as a tty
 * with OPOST and ONLCR does. Set it when the bytes did not pass through the
 * tty output processing (for example the fast pipe).
 */
enum term_feed_flags {
    TERM_FEED_ONLCR = 1u << 0,
};

TERM_API void term_feed(struct term *t, const char *bytes, size_t len, unsigned flags);

/* Report a focus change. The terminal replies only in focus-event mode. */
TERM_API void term_focus(struct term *t, bool focused);

/* Modes that affect how the application encodes input. */
struct term_modes {
    unsigned keyboard;                   /* kitty keyboard protocol flags */
    enum term_mouse mouse;
    enum term_mouse_encoding mouse_encoding;
    struct term_vector2i grid;           /* columns and rows */
    bool app_cursor;                     /* DECCKM */
    bool app_keypad;                     /* DECKPAM */
    bool backarrow_bs;                   /* DECBKM */
    bool bracketed_paste;
    bool focus_events;
    bool alternate;                      /* the alternate screen is active */
    bool reverse_video;                  /* DECSCNM */
    bool synchronized;                   /* mode 2026 */
};

struct term_cursor {
    struct term_vector2i pos;
    enum term_cursor_style style;
    bool visible;
    bool blink;
};

TERM_API struct term_vector2i term_size(const struct term *t);
TERM_API struct term_modes term_modes(const struct term *t);

/*
 * Encode an input event as the bytes the program expects. Get modes from
 * term_modes(). Record ev in keyboard with term_keyboard_update() first. Send
 * the bytes to the program yourself.
 */
TERM_API struct term_input_result term_input_encode_key(
    const struct term_keyboard_state *keyboard,
    const struct term_key_event *ev,
    const struct term_modes *modes,
    char *buf, size_t capacity
);

TERM_API struct term_input_result term_input_encode_mouse(
    const struct term_mouse_event *ev,
    const struct term_modes *modes,
    char *buf, size_t capacity
);

/* Bytes term_input_encode_paste() adds to the text at most. */
#define TERM_PASTE_EXTRA 12

/*
 * Encode pasted text. Drop control characters and bidi controls, so the
 * program sees only what the user saw. Send a line break as CR. Add the
 * bracketed-paste markers when the program asked for them. A buffer of
 * len + TERM_PASTE_EXTRA bytes is always large enough. Text that is empty
 * after the filter gives TERM_INPUT_CONSUMED.
 */
TERM_API struct term_input_result term_input_encode_paste(
    const struct term_modes *modes,
    const char *text, size_t len,
    char *buf, size_t capacity
);
/* The cursor in screen coordinates (not the viewport). */
TERM_API struct term_cursor term_cursor(const struct term *t);
/* Owned, NUL-terminated text from OSC 7 and OSC 22. NULL when unavailable
 * or allocation fails. The strings stay valid after the terminal changes
 * or is freed. Release them with term_text_free(). */
TERM_API char *term_cwd(const struct term *t);
TERM_API char *term_pointer_shape(const struct term *t);
/* Release any owned text returned by the library. NULL is safe. */
TERM_API void term_text_free(char *text);

/*
 * Viewport. The viewport shows as many rows as the screen. Offset 0 shows
 * the live screen; a larger offset shows that many rows of history above it.
 * The alternate screen has no history, so its offset is always 0.
 */
struct term_scrollback {
    int offset;     /* rows between the viewport and the live screen */
    int total;      /* history rows at the current width */
};

TERM_API struct term_scrollback term_scrollback(const struct term *t);
/* Scroll the viewport. A positive count moves back into history. */
TERM_API void term_scroll(struct term *t, int lines);
TERM_API void term_scroll_to(struct term *t, int offset);

/*
 * Selection, in viewport coordinates. A selection starts at one cell and
 * extends to another; the unit widens both ends to words or whole lines.
 * The terminal clears the selection when the text under it changes.
 */
enum term_select_unit {
    TERM_SELECT_CELL,
    TERM_SELECT_WORD,
    TERM_SELECT_LINE,
};

/* Start a selection at cell. For TERM_SELECT_CELL, right_half means the
 * pointer is on the right half of the cell, so the selection starts after it. */
TERM_API void term_select_start(struct term *t, struct term_vector2i cell, bool right_half,
                       enum term_select_unit unit);
/* Extend the selection from its start to cell. */
TERM_API void term_select_extend(struct term *t, struct term_vector2i cell, bool right_half);
TERM_API void term_select_clear(struct term *t);
TERM_API bool term_has_selection(const struct term *t);
/* Owned, NUL-terminated UTF-8 of the selection. NULL when nothing is
 * selected or allocation fails; a selection of blanks may produce an empty
 * string. Capture is atomic with respect to other calls on t. Release the
 * result with term_text_free(). */
TERM_API char *term_selection_text(const struct term *t);
/* Owned OSC 8 link or detected URL at a viewport cell. NULL when there is
 * no link or allocation fails. Release the result with term_text_free(). */
TERM_API char *term_link_at(const struct term *t, struct term_vector2i cell);

/* Cell attributes share the write core's bit layout. Underline styles are
 * mutually exclusive flags, not a shifted enum; use term_attr_underline(). */
enum term_attr {
    TERM_ATTR_BOLD = 1u << 0,
    TERM_ATTR_ITALIC = 1u << 1,
    TERM_ATTR_UNDERLINE = 1u << 2,
    TERM_ATTR_STRIKE = 1u << 3,
    TERM_ATTR_OVERLINE = 1u << 4,
    TERM_ATTR_EMOJI = 1u << 5,        /* the text requested emoji presentation */
    TERM_ATTR_TEXT = 1u << 6,         /* the text requested text presentation */
    TERM_ATTR_FAINT = 1u << 10,
    TERM_ATTR_DOUBLE_UNDERLINE = 1u << 11,
    TERM_ATTR_CURLY_UNDERLINE = 1u << 12,
    TERM_ATTR_DOTTED_UNDERLINE = 1u << 13,
    TERM_ATTR_DASHED_UNDERLINE = 1u << 14,
    TERM_ATTR_LINK = 1u << 15,
};

#define TERM_ATTR_UNDERLINE_MASK \
    (TERM_ATTR_UNDERLINE | TERM_ATTR_DOUBLE_UNDERLINE | TERM_ATTR_CURLY_UNDERLINE | \
     TERM_ATTR_DOTTED_UNDERLINE | TERM_ATTR_DASHED_UNDERLINE)

enum term_underline {
    TERM_UNDERLINE_NONE,
    TERM_UNDERLINE_SINGLE,
    TERM_UNDERLINE_DOUBLE,
    TERM_UNDERLINE_CURLY,
    TERM_UNDERLINE_DOTTED,
    TERM_UNDERLINE_DASHED,
};

static inline enum term_underline term_attr_underline(uint16_t attrs)
{
    if (attrs & TERM_ATTR_DOUBLE_UNDERLINE) return TERM_UNDERLINE_DOUBLE;
    if (attrs & TERM_ATTR_CURLY_UNDERLINE) return TERM_UNDERLINE_CURLY;
    if (attrs & TERM_ATTR_DOTTED_UNDERLINE) return TERM_UNDERLINE_DOTTED;
    if (attrs & TERM_ATTR_DASHED_UNDERLINE) return TERM_UNDERLINE_DASHED;
    return attrs & TERM_ATTR_UNDERLINE ? TERM_UNDERLINE_SINGLE : TERM_UNDERLINE_NONE;
}

/* text refers to a grapheme cluster in the snapshot; see term_snapshot_cluster(). */
#define TERM_TEXT_CLUSTER 0x80000000u

/* One cell as a snapshot shows it. */
struct term_cell {
    uint32_t text;      /* a code point, TERM_TEXT_CLUSTER | n, or 0 for an empty cell */
    term_color fg, bg;
    uint16_t attrs;     /* enum term_attr flags; at most one underline flag */
    uint8_t width;      /* 1; 2 for a wide glyph; 0 for the right half of a wide glyph */
    uint8_t reserved;
};

#ifdef __cplusplus
static_assert(sizeof(struct term_cell) == 16, "four cells fill one 64-byte line");
#else
_Static_assert(sizeof(struct term_cell) == 16, "four cells fill one 64-byte line");
#endif

/*
 * Snapshot: a copy of the viewport for a renderer. It holds no pointer into
 * the terminal, so it stays valid while the terminal changes. One terminal
 * may have several snapshots, for example a window and a tab preview.
 */
TERM_API struct term_snapshot *term_snapshot_new(void);
TERM_API void term_snapshot_free(struct term_snapshot *s);

/* Copy the viewport of t into s. Keep rows with unchanged content keys.
 * Update the history view index and refine counts for visible wide lines.
 * Return false when memory runs out. The snapshot is then empty. */
TERM_API bool term_snapshot_update(struct term_snapshot *s, struct term *t);

/* Palette entries of struct term_view.palette after the 256 indexed colors. */
enum {
    TERM_PALETTE_FG = 256,
    TERM_PALETTE_BG = 257,
    TERM_PALETTE_CURSOR = 258,
    TERM_PALETTE_SIZE = 259,
};

struct term_view {
    struct term_vector2i size;
    struct term_cursor cursor;  /* viewport coordinates; not visible when scrolled away */
    int scroll_offset;
    /* Rows the content moved up since the previous update, when that movement
     * explains the change; otherwise 0. */
    int scrolled;
    bool reverse_video;
    /* Changes when any part of the view changes. */
    uint64_t version;
    /* Changes when a palette entry changes. */
    uint64_t palette_version;
    const uint32_t *palette;    /* TERM_PALETTE_SIZE ARGB entries */
};

TERM_API const struct term_view *term_snapshot_view(const struct term_snapshot *s);
/* The cells of viewport row y: view->size.x entries. */
TERM_API const struct term_cell *term_snapshot_row(const struct term_snapshot *s, int y);
/* An identity for the content of row y. Two rows with the same key hold the
 * same cells, also when the content moved to another row. */
TERM_API uint64_t term_snapshot_row_key(const struct term_snapshot *s, int y);

/* Number of rows in history above the screen. 0 if alternate screen or no history. */
TERM_API int term_history_rows(const struct term *t);
/* Owned, NUL-terminated UTF-8 of up to max_rows history rows before the
 * current viewport. Join soft-wrapped rows and end closed lines with a
 * newline. Does not change the selection. No history or max_rows <= 0 gives
 * an empty string; NULL means allocation failed or t is NULL. Release the
 * result with term_text_free(). */
TERM_API char *term_history_text(struct term *t, int max_rows);
TERM_API struct term_span term_snapshot_row_selection(const struct term_snapshot *s, int y);

/* The code points of a cluster cell. Returns the number of code points and
 * writes at most cap of them. */
TERM_API int term_snapshot_cluster(const struct term_snapshot *s, uint32_t text, uint32_t *cps, int cap);

/* The ARGB value of a color in a view. */
static inline uint32_t term_view_color(const struct term_view *v, term_color c)
{
    if (!term_color_is_slot(c))
        return c;
    return v->palette[c & TERM_COLOR_SLOT_INDEX];
}

#ifdef __cplusplus
}
#endif

#endif