frontend: add a line editor for shell input

frontend/line-ed/line-ed.h

@@ -0,0 +1,96 @@
+#ifndef LINE_ED_H_
+#define LINE_ED_H_
+
+#define LINE_MAX 4096
+
+#include "tty.h"
+
+#include <blue/core/queue.h>
+#include <blue/object/array.h>
+#include <ivy/line-source.h>
+#include <stddef.h>
+
+struct s_tty_vmode;
+
+struct line_ed;
+
+struct line_ed_hook {
+	void (*hook_keypress)(struct line_ed *, struct line_ed_hook *, s_keycode);
+	void (*hook_buffer_modified)(struct line_ed *, struct line_ed_hook *);
+	b_queue_entry hook_entry;
+};
+
+enum line_ed_flags {
+	/* always reprint an entire line when a character is added/deleted.
+	 * without this flag, only the modified character any subsequent
+	 * characters are reprinted. */
+	LINE_ED_FULL_REPRINT = 0x01u,
+
+	/* keep line continuation (backslash-newline) tokens in the output
+	 * buffer (default behaviour) */
+	LINE_ED_KEEP_CONTINUATIONS = 0x00u,
+	/* convert line continuation tokens in the output buffer to simple
+	 * linefeeds. */
+	LINE_ED_CONVERT_CONTINUATIONS = 0x02u,
+	/* remove line continuation tokens from the output buffer, so that all
+	 * chars are on a single line */
+	LINE_ED_REMOVE_CONTINUATIONS = 0x06u,
+};
+
+struct line_ed {
+	enum line_ed_flags l_flags;
+
+	/* array of basic prompt strings */
+	const char *l_prompt[2];
+	/* input buffer, pointer to the buffer cell that corresponds to
+	 * the current cursor position, and pointer to the byte AFTER the last
+	 * usable byte in the buffer */
+	char *l_buf, *l_buf_ptr, *l_buf_end;
+	/* pointer to the byte AFTER the last byte of the user's input */
+	char *l_line_end;
+	/* 2-dimensional coordinates of the current cursor position.
+	 * this does NOT include any prompts that are visible on the terminal */
+	unsigned int l_cursor_x, l_cursor_y;
+	/* the number of line continuations that have been inputted */
+	unsigned int l_continuations;
+
+	struct ivy_line_source l_line_source;
+
+	/* the lexical scope that we are currently in.
+	 * this is provided by components further up the input pipeline,
+	 * for example, when we are inside a string or if-statement. */
+	const char *l_scope_type;
+
+	/* array of previously entered commands */
+	b_array *l_history;
+	/* index of the currently selected history entry */
+	unsigned int l_history_pos;
+
+	/* list of defined highlight ranges */
+	b_queue l_hl_ranges;
+	/* list of installed hooks */
+	b_queue l_hooks;
+};
+
+extern struct line_ed *line_ed_create(void);
+extern void line_ed_destroy(struct line_ed *ed);
+extern void line_ed_set_flags(struct line_ed *ed, enum line_ed_flags flags);
+extern void line_ed_set_scope_type(struct line_ed *ed, const char *scope_type);
+
+extern void line_ed_put_highlight(
+	struct line_ed *ed, unsigned long start_x, unsigned long start_y,
+	unsigned long end_x, unsigned long end_y, const struct s_tty_vmode *vmode);
+extern void line_ed_clear_highlights(struct line_ed *ed);
+extern void line_ed_print_highlights(struct line_ed *ed);
+
+extern void line_ed_add_hook(struct line_ed *ed, struct line_ed_hook *hook);
+extern void line_ed_remove_hook(struct line_ed *ed, struct line_ed_hook *hook);
+
+extern long line_ed_readline(struct line_ed *ed, char *out, size_t max);
+
+static inline struct ivy_line_source *line_ed_to_line_source(struct line_ed *ed)
+{
+	return &ed->l_line_source;
+}
+
+#endif