Add spreadsheet program

.clang-format

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+
+# modified .clang-format from
+# https://github.com/torvalds/linux/blob/master/.clang-format
+
+AccessModifierOffset: -4
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: false
+AlignConsecutiveDeclarations: false
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+AlwaysBreakAfterDefinitionReturnType: true
+AlwaysBreakAfterReturnType: None
+AlwaysBreakBeforeMultilineStrings: false
+AlwaysBreakTemplateDeclarations: false
+BinPackArguments: true
+BinPackParameters: true
+BraceWrapping:
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+  AfterControlStatement: false
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+  AfterNamespace: true
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+BreakBeforeBraces: Custom
+BreakBeforeInheritanceComma: false
+BreakBeforeTernaryOperators: false
+BreakConstructorInitializersBeforeComma: false
+BreakConstructorInitializers: BeforeComma
+BreakAfterJavaFieldAnnotations: false
+BreakStringLiterals: false
+ColumnLimit: 80
+CommentPragmas: '^ IWYU pragma:'
+CompactNamespaces: false
+ConstructorInitializerAllOnOneLineOrOnePerLine: false
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+ContinuationIndentWidth: 4
+Cpp11BracedListStyle: false
+DerivePointerAlignment: false
+DisableFormat: false
+ExperimentalAutoDetectBinPacking: false
+FixNamespaceComments: false
+
+
+IncludeBlocks: Preserve
+IncludeCategories:
+  - Regex: '.*'
+    Priority: 1
+IncludeIsMainRegex: '(Test)?$'
+IndentCaseLabels: false
+IndentGotoLabels: false
+IndentPPDirectives: None
+IndentWidth: 4
+IndentWrappedFunctionNames: false
+JavaScriptQuotes: Leave
+JavaScriptWrapImports: true
+KeepEmptyLinesAtTheStartOfBlocks: false
+MacroBlockBegin: ''
+MacroBlockEnd: ''
+MaxEmptyLinesToKeep: 1
+NamespaceIndentation: None
+ObjCBinPackProtocolList: Auto
+ObjCBlockIndentWidth: 4
+ObjCSpaceAfterProperty: true
+ObjCSpaceBeforeProtocolList: true
+
+# Taken from git's rules
+PenaltyBreakAssignment: 10
+PenaltyBreakBeforeFirstCallParameter: 30
+PenaltyBreakComment: 10
+PenaltyBreakFirstLessLess: 0
+PenaltyBreakString: 10
+PenaltyExcessCharacter: 100
+PenaltyReturnTypeOnItsOwnLine: 60
+
+PointerAlignment: Right
+ReflowComments: false
+SortIncludes: false
+SortUsingDeclarations: false
+SpaceAfterCStyleCast: false
+SpaceAfterTemplateKeyword: true
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeCtorInitializerColon: true
+SpaceBeforeInheritanceColon: true
+SpaceBeforeParens: ControlStatementsExceptForEachMacros
+SpaceBeforeRangeBasedForLoopColon: true
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 1
+SpacesInAngles: false
+SpacesInContainerLiterals: false
+SpacesInCStyleCastParentheses: false
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+TabWidth: 4

.gitignore

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+bin
+obj
+.vscode

ISSUES

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+
+Missing features
+----------------
+
+- [x] 1. Implement working cell edit function
+- [x] 2. Add type detection in cells
+	- [x] int64, long double, text
+	- [ ] date, functions
+- [ ] 3. Add text parsing in cells
+	- [x] parse types
+	- [ ] parse functions
+- [ ] 4. Add file saving/loading
+- [ ] 5. Implement scrolling
+
+
+
+Medium priority
+---------------
+
+- Date/time support in cells
+- Extend type detection
+
+
+Low priority
+------------
+
+[1.]
+- Avoid realloc on each append/pop when editing text in interface.c/editor_backspace()
+
+[misc.]
+- Decide and implement data structure for insertion/search of cells (currently BST, maybe red-black-tree?)
+- Use BST magic to find relevant subtree to print given a scroll_x and scroll_y
+- Remove cells from BST when they are empty

Makefile

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+
+CC	   := gcc
+CFLAGS   := -O0 -g -Wall -Wextra -fanalyzer \
+		    -fsanitize=address -fno-omit-frame-pointer
+LDFLAGS  := -g -fsanitize=address
+LDLIBS   := -lncurses
+
+SRC_DIR := src
+OBJ_DIR := obj
+BIN_DIR := bin
+
+EXE := $(BIN_DIR)/run
+SRC := $(wildcard $(SRC_DIR)/*.c)
+OBJ := $(SRC:$(SRC_DIR)/%.c=$(OBJ_DIR)/%.o)
+
+.PHONY: all clean
+
+all: $(EXE)
+
+$(EXE): $(OBJ) | $(BIN_DIR)
+	$(CC) $(LDFLAGS) $^ $(LDLIBS) -o $@
+
+$(OBJ_DIR)/%.o: $(SRC_DIR)/%.c | $(OBJ_DIR)
+	$(CC) $(CPPFLAGS) $(CFLAGS) -c $< -o $@
+
+$(BIN_DIR) $(OBJ_DIR):
+	mkdir -p $@
+
+clean:
+	@$(RM) -rv $(BIN_DIR) $(OBJ_DIR)
+
+-include $(OBJ:.o=.d)

README.md

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+
+# Terminal spreadsheet
+
+![spreadsheet2](https://user-images.githubusercontent.com/82065181/209571188-7c1e90ca-d7f4-4de7-adc4-64000e6bf0f2.png)
+
+This is a WIP spreadsheet application for the terminal using ncurses.
+See [ISSUES](ISSUES) to get an idea of what needs to be implemented.
+
+## Download and build
+```sh
+git clone https://github.com/olemorud/terminal-spreadsheet.git
+cd terminal-spreadsheet
+make
+```
+
+## Run
+```sh
+cd bin
+./run
+```

src/book.c

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+#include "book.h"
+#include "config.h"
+#include <err.h>
+#include <stdlib.h>
+#include <string.h>
+
+void book_init(struct book *b, char *title)
+{
+    b->n_sheets = 0;
+    b->sheets = malloc(0);
+    if (!book_add_sheet(b))
+        exit(1);
+
+    (b->sheets)[1] = NULL;
+
+    if (title != NULL)
+        b->title = strndup(title, MAX_STR);
+    else
+        b->title = strdup("");
+}
+
+void book_delete(struct book *b)
+{
+    if (b == NULL) {
+        warn("attempted to delete NULL book");
+        return;
+    }
+
+    size_t i = 0;
+    while ((b->sheets)[i] != NULL) {
+        sheet_delete((b->sheets)[i]);
+        i++;
+    }
+}
+
+bool book_add_sheet(struct book *b)
+{
+    struct sheet *s;
+
+    b->n_sheets++;
+
+    void* tmp = realloc(b->sheets, sizeof(struct sheet*) * (b->n_sheets + 1));
+    if (tmp == NULL)
+        return false;
+    b->sheets = tmp;
+
+    b->sheets[b->n_sheets] = NULL;
+
+    s = malloc(sizeof(struct sheet));
+    sheet_init(s, DEFAULT_WIDTH, DEFAULT_HEIGHT, DEFAULT_SHEET_TITLE);
+
+    b->sheets[b->n_sheets-1] = s;
+
+    return true;
+}

src/book.h

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+#ifndef BOOK_H
+#define BOOK_H
+
+#include "sheet.h"
+#include <stdbool.h>
+#include <stddef.h>
+
+struct book {
+    struct sheet **sheets;
+    size_t         n_sheets;
+    char          *title;
+};
+
+void book_init(struct book *b, char *title);
+
+void book_delete(struct book *b);
+
+bool book_add_sheet(struct book *b);
+
+#endif

src/cell.c

@@ -0,0 +1,52 @@
+#include "cell.h"
+#include <stdlib.h>
+#include <err.h>
+#include <string.h>
+
+void cell_parse_function(struct cell *cell);
+
+void cell_init(struct cell *c, size_t x, size_t y, enum cell_type type)
+{
+    c->referenced_by = NULL;
+    c->x_pos = x;
+    c->y_pos = y;
+    c->type = type;
+    c->text = calloc(1,1);
+    c->value.integer = 0;
+}
+
+void cell_delete(struct cell *c)
+{
+    if (c == NULL) {
+        warn("attempted to delete NULL cell");
+        return;
+    }
+
+    free(c->text);
+    free(c);
+}
+
+void cell_set_type(struct cell *cell)
+{
+    if (cell->text[0] == '=') {
+        //cell_parse_function(cell);
+        return;
+    }
+
+    char *endptr;
+    int i = strtoll(cell->text, &endptr, 10);
+
+    if (*endptr == '\0') {
+        cell->type = Integer;
+        cell->value.integer = i;
+        return;
+    }
+
+    int d = strtold(cell->text, &endptr);
+
+    if (*endptr == '\0') {
+        cell->type = Floating;
+        cell->value.floating = d;
+        return;
+    }
+}

src/cell.h

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+#ifndef CELL_H
+#define CELL_H
+
+#include <stddef.h>
+#include <stdint.h>
+#include <time.h>
+#include "common.h"
+
+enum cell_type {
+    Text,
+    Integer,
+    Floating,
+    Date
+};
+
+struct cell_list {
+    struct cell      *cell;
+    struct cell_list *next;
+};
+
+struct cell {
+    struct cell_list *referenced_by;
+    size_t            x_pos;
+    size_t            y_pos;
+    char             *text;
+    enum cell_type    type;
+    union {
+        int64_t integer;
+        double  floating;
+        time_t  date;
+    } value;
+};
+
+void cell_init(struct cell *c, size_t x_pos, size_t y_pos, enum cell_type type);
+void cell_delete(struct cell *c);
+void cell_set_type(struct cell *cell);
+
+#endif

src/celltree.c

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+#include "celltree.h"
+#include <stdlib.h>
+#include <errno.h>
+#include <err.h>
+
+/* returns true if (ax,ay) `greater than` (bx,by) */
+static bool greater_than(int x_a, int y_a, int x_b, int y_b)
+{
+    if (x_a == x_b)
+        return y_a > y_b;
+
+    return x_a > x_b;
+}
+
+void celltree_delete(struct celltree *root)
+{
+    if (root == NULL) {
+        return;
+    }
+
+    cell_delete(root->cell);
+    celltree_delete(root->right);
+    celltree_delete(root->left);
+
+    free(root);
+}
+
+struct cell* celltree_search(struct celltree *root, size_t x, size_t y)
+{
+    if (root == NULL) {
+        return NULL;
+    }
+
+    struct cell *c = root->cell;
+
+    if (c->x_pos == x && c->y_pos == y) {
+        return root->cell;
+    }
+
+    if (greater_than(x, y, c->x_pos, c->y_pos)) {
+        return celltree_search(root->right, x, y);
+    } else {
+        return celltree_search(root->left, x, y);
+    }
+}
+
+void celltree_insert(struct celltree **root, struct cell *c)
+{
+    if (*root == NULL) {
+        *root = malloc(sizeof **root);
+        if (*root == NULL)
+            exit(errno);
+        (*root)->cell = c;
+        (*root)->right = NULL;
+        (*root)->left = NULL;
+        return;
+    }
+
+    if (greater_than(c->x_pos, c->y_pos, (*root)->cell->x_pos,
+                     (*root)->cell->y_pos)) {
+        celltree_insert(&(*root)->right, c);
+    } else {
+        celltree_insert(&(*root)->left, c);
+    }
+}

src/celltree.h

@@ -0,0 +1,21 @@
+#ifndef CELLTREE_H
+#define CELLTREE_H
+
+#include <stdbool.h>
+#include "cell.h"
+
+/* TODO: implement red-black tree */
+struct celltree {
+    struct cell     *cell;
+    struct celltree *right;
+    struct celltree *left;
+    bool             isRed;
+};
+
+void celltree_delete(struct celltree *root);
+
+struct cell *celltree_search(struct celltree *root, size_t x, size_t y);
+
+void celltree_insert(struct celltree **root, struct cell *c);
+
+#endif

src/common.h

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+
+#ifndef COMMON_H
+#define COMMON_H
+
+enum modes {Edit, Command, G};
+
+#endif

src/config.h

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+
+#ifndef CONFIG_H
+#define CONFIG_H
+
+// strings
+#define DEFAULT_BOOK_TITLE  "Untitled"
+#define DEFAULT_SHEET_TITLE "Sheet "
+#define DEFAULT_HEIGHT      40
+#define DEFAULT_WIDTH       80
+#define MAX_STR             64
+
+
+// dimensions
+#define CELL_SIZE 12
+#define TAB_SIZE 24
+#define Y_AXIS_WIDTH 4
+#define N_CELLS_WIDTH 5
+#define N_CELLS_HEIGHT 5
+
+
+// colors
+#define COLOR_TITLE 20
+#define COLOR_BACKGROUND 21
+#define COLOR_LIGHTER_GRAY 22
+#define COLOR_LIGHT_GRAY 23
+#define COLOR_GRAY 24
+#define COLOR_HIGHLIGHTED 25
+#define COLOR_EDITMODE 26
+
+#endif

src/draw.c

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+
+#include "draw.h"
+#include "cell.h"
+#include "celltree.h"
+#include "config.h"     // colors, sizes ...
+#include "sheet.h"      // struct sheet
+#include <ncurses.h>    // ncurses functions
+#include <signal.h>     // handle sigterm
+#include <string.h>     // strlen
+
+#define _STR(x) #x
+#define STR(x) _STR(x)
+
+static void cleanup()
+{
+    clear();
+    echo();
+    curs_set(1);
+    refresh();
+    endwin();
+}
+
+static int x_pos(int x)
+{
+    return x * CELL_SIZE + Y_AXIS_WIDTH;
+}
+
+static int y_pos(int y)
+{
+    return y + 2;
+}
+
+static int get_cell_color(int const row, int const col)
+{
+    return (row + col) % 2 ? COLOR_LIGHTER_GRAY : COLOR_LIGHT_GRAY;
+}
+
+void draw_init(struct book *book)
+{
+    initscr();
+    atexit(cleanup);
+    signal(SIGTERM, exit);
+    noecho();
+    cbreak();
+    keypad(stdscr, true);
+
+    set_escdelay(0);
+    curs_set(0);
+
+    start_color();
+    init_color(COLOR_LIGHTER_GRAY, 900, 900, 900);
+    init_pair(COLOR_LIGHTER_GRAY, COLOR_BLACK, COLOR_LIGHTER_GRAY);
+
+    init_color(COLOR_LIGHT_GRAY, 800, 800, 800);
+    init_pair(COLOR_LIGHT_GRAY, COLOR_BLACK, COLOR_LIGHT_GRAY);
+
+    init_color(COLOR_GRAY, 650, 650, 650);
+    init_pair(COLOR_GRAY, COLOR_BLACK, COLOR_GRAY);
+
+    init_color(COLOR_HIGHLIGHTED, 800, 600, 600);
+    init_pair(COLOR_HIGHLIGHTED, COLOR_BLACK, COLOR_HIGHLIGHTED);
+
+    init_color(COLOR_EDITMODE, 600, 800, 600);
+    init_pair(COLOR_EDITMODE, COLOR_BLACK, COLOR_EDITMODE);
+
+    init_pair(COLOR_TITLE, COLOR_BLACK, COLOR_GREEN);
+
+    init_pair(COLOR_BACKGROUND, COLOR_MAGENTA, COLOR_GREEN);
+
+    bkgdset(COLOR_PAIR(COLOR_BACKGROUND));
+
+    draw_book(book, 0);
+
+    draw_highlight(0, 0);
+    draw_right_status("Normal");
+
+    refresh();
+}
+
+void draw_cell(struct cell const * const cell)
+{
+    int x = x_pos(cell->x_pos);
+    int y = y_pos(cell->y_pos);
+
+    int color = get_cell_color(y, x);
+
+    move(y, x);
+
+    attron(COLOR_PAIR(color));
+
+    switch(cell->type){
+        case Integer:
+            printw("%" STR(CELL_SIZE) "li", cell->value.integer);
+            break;
+        case Floating:
+            printw("%" STR(CELL_SIZE) "lf", cell->value.floating);
+            break;
+        default:
+            printw("%-" STR(CELL_SIZE) "s", cell->text);
+            break;
+    }
+
+    attroff(COLOR_PAIR(color));
+}
+
+static void draw_celltree(struct celltree const *const root)
+{
+    if (root == NULL) {
+        return;
+    }
+
+    draw_cell(root->cell);
+    draw_celltree(root->right);
+    draw_celltree(root->left);
+}
+
+static void draw_row_num(int n)
+{
+    attron(COLOR_PAIR(COLOR_GRAY));
+    printw("%" STR(Y_AXIS_WIDTH) "d", n);
+    attroff(COLOR_PAIR(COLOR_GRAY));
+}
+
+static void draw_row_header(int row)
+{
+    // TODO: make it dynamic
+    char buf[4] = "   ";
+    int i = sizeof buf - 2;
+    row++;
+
+    while (row && i >= 0) {
+        buf[i] = (row % 26) + 'A' - 1;
+        row /= 26;
+        i--;
+    }
+
+    attron(COLOR_PAIR(COLOR_GRAY));
+    printw("%" STR(CELL_SIZE) "s", buf);
+    attroff(COLOR_PAIR(COLOR_GRAY));
+}
+
+static void draw_sheet(struct sheet *s)
+{
+    addch('\n');
+
+    int width = getmaxx(stdscr) - Y_AXIS_WIDTH;
+    int n_cells_wide = width / CELL_SIZE;
+    int n_cells_tall = getmaxy(stdscr) - 3;
+
+    // print row headers
+    chgat(Y_AXIS_WIDTH, 0, COLOR_GRAY, NULL);
+    for (int i = 0; i < n_cells_wide; i++) {
+        draw_row_header(i);
+    }
+
+    // clear sheet before drawing on top
+    for (int row = 0; row < n_cells_tall; row++) {
+        int color;
+        addch('\n');
+        draw_row_num(row);
+
+        for (int col = 0; col < n_cells_wide; col++) {
+            color = get_cell_color(row, col);
+
+            attron(COLOR_PAIR(color));
+
+            mvprintw(y_pos(row),
+                    x_pos(col),
+                    "%" STR(CELL_SIZE) "s", " ");
+        }
+        attroff(COLOR_PAIR(color));
+    }
+    
+    // draw on top of empty sheet
+    draw_celltree(s->root_cell);
+}
+
+static void draw_input_bar()
+{
+    int width, height;
+
+    getmaxyx(stdscr, height, width);
+
+    move(height - 1, 0);
+
+    attron(COLOR_PAIR(COLOR_TITLE));
+    for (int i = 0; i < width; i++) {
+        addch(' ');
+    }
+}
+
+void draw_book(struct book *book, size_t tab)
+{
+    move(0, 0);
+    attron(COLOR_PAIR(COLOR_TITLE));
+    printw(" %s ", book->title);
+    attroff(COLOR_PAIR(COLOR_TITLE));
+
+    for (size_t i = 0; i < book->n_sheets; i++) {
+        int attr = tab == i ? COLOR_GRAY : COLOR_LIGHT_GRAY;
+        attron(COLOR_PAIR(attr));
+        printw("%10s ", book->sheets[i]->title);
+        attroff(COLOR_PAIR(attr));
+    }
+
+    draw_sheet(book->sheets[tab]);
+
+    draw_input_bar();
+}
+
+/* highlights relative to screen */
+void draw_highlight(int const x, int const y)
+{
+    static int prev_x;
+    static int prev_y;
+    int color;
+
+    mvchgat(y_pos(y), x_pos(x), CELL_SIZE, 0, COLOR_HIGHLIGHTED,
+            NULL);
+
+    color = get_cell_color(prev_y, prev_x);
+
+    mvchgat(y_pos(prev_y), x_pos(prev_x), CELL_SIZE, 0, color, NULL);
+
+    prev_x = x;
+    prev_y = y;
+}
+
+void draw_left_status(char const *const s)
+{
+    int y = getmaxy(stdscr);
+
+    attron(COLOR_PAIR(COLOR_TITLE));
+    mvprintw(y - 1, 1, "%s", s);
+    attron(COLOR_PAIR(COLOR_TITLE));
+}
+
+void draw_right_status(char const *const s)
+{
+    int x, y;
+    getmaxyx(stdscr, y, x);
+
+    attron(COLOR_PAIR(COLOR_TITLE));
+    mvprintw(y - 1, x - 1 - strlen(s), "%s", s);
+    attron(COLOR_PAIR(COLOR_TITLE));
+}
+

src/draw.h

@@ -0,0 +1,21 @@
+
+#ifndef DRAW_H
+#define DRAW_H
+
+#include "book.h"
+#include <stddef.h>
+#include "cell.h"
+
+void draw_highlight(int const x, int const y);
+
+void draw_init(struct book *book);
+
+void draw_book(struct book *b, size_t tab);
+
+void draw_cell(struct cell const * const cell);
+
+void draw_left_status(const char *const s);
+
+void draw_right_status(char const *const s);
+
+#endif

src/function_parse.c

@@ -0,0 +1,147 @@
+
+#include <ctype.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <errno.h>
+
+static char *operators[] = {
+    "+",
+    "-",
+    "*",
+    "/",
+    ">",
+    "<",
+    NULL,
+};
+
+static char *separators[] = {
+    ",",
+    "(",
+    ")",
+    NULL,
+};
+
+enum type {
+    error,
+    operator,
+    separator,
+    identifier,
+    number,
+};
+
+struct token {
+    char const *   value;
+    size_t         value_len;
+    enum type type;
+};
+
+struct token_list {
+    struct token *tokens;
+    size_t len;
+    char *error_msg;
+};
+
+// returns length of string in haystack matching needle, or 0 if it
+// doesn't exist
+static int contains(char * const *haystack, char* needle)
+{
+    for(char *s = *haystack; s; s++){
+        if (strcmp(s, needle) == 0) {
+            return strlen(s);
+        }
+    }
+
+    return false;
+}
+
+static struct token eat(char **str, int (*f)(int), enum type type)
+{
+    struct token tok;
+    tok.type = type;
+    tok.value = *str;
+    tok.value_len = 0;
+
+    while (f(**str)) {
+        *str += 1;
+        tok.value_len += 1;
+    }
+
+    return tok;
+}
+
+static struct token tokenize_identifier(char** str)
+{
+    return eat(str, isalnum, identifier);
+}
+
+static struct token tokenize_number(char **str)
+{
+    return eat(str, isdigit, identifier);
+}
+
+// Returns a token array from function
+static struct token_list tokenize(char *str)
+{
+    struct token_list *tok_list = malloc(sizeof *tok_list);
+
+    if (tok_list == NULL) {
+        exit(errno);
+    }
+
+    const size_t max_tok = 16; // TODO: dynamically grow array
+
+    tok_list->tokens = malloc(sizeof *(tok_list->tokens) * max_tok);
+    if (tok_list->tokens == NULL)
+        exit(errno);
+    tok_list->len = 0;
+
+    // identifiers start with letters but can contain numbers
+    while (*str && tok_list->len < max_tok) {
+        struct token t;
+        size_t n;
+
+        if (isalpha(*str)) {
+             t = tokenize_identifier(&str);
+        }
+        else if (!isalnum(*str) ) {
+            t = tokenize_number(&str);
+        }
+        else if ((n = contains(operators, str))) {
+            t.type = operator;
+            t.value = str;
+            t.value_len = n;
+        }
+        else if ((n = contains(separators, str))) {
+            t.type = separator;
+            t.value = str;
+            t.value_len = n;
+        }
+        else {
+            t.type = error;
+            t.value = str;
+            t.value_len = strlen(str);
+        }
+    
+        tok_list->tokens[tok_list->len] = t;
+        tok_list->len += 1;
+    }
+
+    return *tok_list;
+}
+
+// credits: Daniel J. Bernstein 
+// https://web.archive.org/web/20220328102559/http://www.cse.yorku.ca/~oz/hash.html
+static unsigned long hash(unsigned char *str)
+{
+    unsigned long hash = 5381;
+    int c = 0;
+
+    for(size_t i=0; str[i] != '\0'; i++)
+        hash = hash * 33 + c;
+
+    return hash;
+}
+
+

src/function_parse.h

@@ -0,0 +1,7 @@
+
+#ifndef FUNCTION_PARSE_H
+#define FUNCTION_PARSE_H
+
+
+
+#endif

src/interface.c

@@ -0,0 +1,166 @@
+
+#include "interface.h"
+#include "cell.h"
+#include <curses.h>
+#include <stdlib.h>
+#include "celltree.h"
+#include "keymap.h"
+#include "draw.h"
+
+int g_display_sel_x = 0;
+int g_display_sel_y = 0;
+int g_tab = 0;
+//int g_right_scrolled = 0;
+//int g_down_scrolled = 0;
+
+struct book *g_book = NULL;
+struct cell *g_cur = NULL;
+
+enum modes mode = Command;
+
+void interface_attach(struct book *b)
+{
+    g_book = b;
+}
+
+void interface_move_right()
+{
+    g_display_sel_x++;
+    draw_highlight(g_display_sel_x, g_display_sel_y);
+}
+
+void interface_move_left()
+{
+    if (g_display_sel_x == 0)
+        return;
+
+    g_display_sel_x--;
+    draw_highlight(g_display_sel_x, g_display_sel_y);
+}
+
+void interface_move_up()
+{
+    if (g_display_sel_y == 0)
+        return;
+
+    g_display_sel_y--;
+    draw_highlight(g_display_sel_x, g_display_sel_y);
+}
+
+void interface_move_down()
+{
+    g_display_sel_y++;
+    draw_highlight(g_display_sel_x, g_display_sel_y);
+}
+
+void interface_next_tab()
+{
+    g_tab++;
+    g_tab %= g_book->n_sheets;
+    draw_book(g_book, g_tab);
+}
+
+void interface_prev_tab()
+{
+    g_tab--;
+    if (g_tab < 0) {
+        g_tab = g_book->n_sheets - 1;
+    }
+    draw_book(g_book, g_tab);
+}
+
+void interface_editor_backspace()
+{
+    size_t textlen = strlen(g_cur->text);
+
+    if (textlen == 0)
+        return;
+
+    int x, y;
+
+    addch(' ');
+    getyx(stdscr, y, x);
+    move(y, x - 1);
+
+    g_cur->text = realloc(g_cur->text, textlen);
+    g_cur->text[textlen - 1] = '\0';
+
+    refresh();
+}
+
+void interface_editor_append(const char c)
+{
+    int x, y;
+
+    size_t textlen = strlen(g_cur->text);
+
+    g_cur->text = realloc(g_cur->text, textlen + 2);
+    g_cur->text[textlen] = c;
+    g_cur->text[textlen + 1] = '\0';
+
+    getyx(stdscr, y, x);
+    draw_cell(g_cur);
+    move(y, x);
+    refresh();
+}
+
+static void start_edit_cell()
+{
+    // struct cell* cur
+    g_cur = celltree_search(g_book->sheets[g_tab]->root_cell, g_display_sel_x,
+                        g_display_sel_y);
+
+    if (g_cur == NULL) {
+        g_cur = malloc(sizeof(struct cell));
+        cell_init(g_cur, g_display_sel_x, g_display_sel_y, Text);
+        celltree_insert(&g_book->sheets[g_tab]->root_cell, g_cur);
+    }
+
+    draw_left_status(g_cur->text);
+}
+
+void interface_mode_normal()
+{
+    draw_right_status("Normal");
+    mode = Command;
+    curs_set(0);
+}
+
+void interface_mode_g()
+{
+    draw_right_status("g");
+    mode = G;
+}
+
+void interface_mode_edit()
+{
+    mode = Edit;
+    draw_right_status("Insert");
+    curs_set(1);
+    echo();
+    start_edit_cell();
+}
+
+void interface_commit_cell_change()
+{
+    cell_set_type(g_cur);
+    draw_cell(g_cur);
+}
+
+void interface_handle_resize()
+{
+    draw_book(g_book, g_tab);
+    refresh();
+}
+
+void interface_interact()
+{
+    refresh();
+
+    int x, y;
+    getmaxyx(stdscr, y, x);
+    move(y - 1, x - 1);
+
+    int c = getch();
+    keymap_parse_key(c, mode);
+}

src/interface.h

@@ -0,0 +1,69 @@
+
+#ifndef INTERFACE_H
+#define INTERFACE_H
+
+#include "book.h"
+
+/*  */
+void interface_commit_cell_change();
+
+/* terminal resize handler */
+void interface_handle_resize();
+
+/* attach book to interface */
+void interface_attach(struct book *b);
+
+/* move one cell right */
+void interface_move_right();
+
+/* move one cell left */
+void interface_move_left();
+
+/* move one cell up */
+void interface_move_up();
+
+/* move one cell down */
+void interface_move_down();
+
+/* move to prev tab */
+void interface_prev_tab();
+
+/* move to next tab */
+void interface_next_tab();
+
+/* writes a status message in the bottom
+ * right corner
+ **/
+void interface_write_right_status(char const *const s);
+
+/* event loop */
+void interface_interact();
+
+/*
+ * Insert Mode commands
+ * --------------------
+ */
+
+/* Add char to input */
+void interface_editor_append(const char c);
+
+/* Remove last char */
+void interface_editor_backspace();
+
+
+/*
+ * Mode switching
+ * --------------
+ */
+
+/* switch to g mode TODO: find better way */
+void interface_mode_g();
+
+/* switch to insert mode */
+void interface_mode_edit();
+
+/* switch to normal mode */
+void interface_mode_normal();
+
+
+#endif

src/keymap.c

@@ -0,0 +1,81 @@
+
+#include "keymap.h"
+#include "draw.h"
+#include "interface.h"
+#include <curses.h>
+
+#define KEY_ESC 27
+
+static void * const keymap_always[1024] = {
+    [KEY_RESIZE] = interface_handle_resize,
+    [27] /*ESC*/ = interface_mode_normal,
+};
+
+static void * const keymap_normal[1024] = {
+    ['i']       = interface_mode_edit,
+    ['a']       = interface_mode_edit,
+    ['g']       = interface_mode_g,
+    [KEY_LEFT]  = interface_move_left,
+    ['h']       = interface_move_left,
+    [KEY_DOWN]  = interface_move_down,
+    ['j']       = interface_move_down,
+    [KEY_UP]    = interface_move_up,
+    ['k']       = interface_move_up,
+    [KEY_RIGHT] = interface_move_right,
+    ['l']       = interface_move_right,
+};
+
+static void * const keymap_edit[1024] = {
+    [KEY_ESC]            = interface_mode_normal,
+    [KEY_BACKSPACE] = interface_editor_backspace,
+};
+
+static void * const keymap_g[1024] = {
+    ['t'] = interface_next_tab,
+    ['T'] = interface_prev_tab,
+};
+
+static void undefined()
+{
+    int height = getmaxy(stdscr);
+    move(height - 1, 0);
+    printw("key not defined");
+}
+
+void keymap_parse_key(size_t c, enum modes mode)
+{
+    void (*cmd)(void) = NULL;
+
+    switch (mode) {
+    case Command:
+        cmd = keymap_normal[c];
+        break;
+    case G:
+        cmd = keymap_g[c];
+        break;
+    case Edit:
+        cmd = keymap_edit[c];
+        if (cmd == NULL){
+            interface_editor_append(c);
+            return;
+        }
+        if (c == KEY_ESC) {
+            interface_commit_cell_change();
+        }
+        break;
+    }
+
+    if(mode != Edit) {
+        mode = Command;
+    }
+
+    if (cmd == NULL) {
+        cmd = keymap_always[c];
+
+        if (cmd == NULL) {
+            cmd = undefined;
+        }
+    }
+
+    (*cmd)();
+}

src/keymap.h

@@ -0,0 +1,10 @@
+
+#ifndef KEYMAP_H
+#define KEYMAP_H
+
+#include "common.h"
+#include <stddef.h>
+
+void keymap_parse_key(size_t c, enum modes mode);
+
+#endif

src/main.c

@@ -0,0 +1,33 @@
+#include "book.h"
+#include "draw.h"
+#include "config.h"
+#include "interface.h"
+#include "sheet.h"
+#include <curses.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+
+int main(int argc, char **argv)
+{
+    (void)argv;
+    (void)argc;
+
+    struct book b;
+
+    book_init(&b, DEFAULT_BOOK_TITLE);
+
+    book_add_sheet(&b);
+    book_add_sheet(&b);
+    book_add_sheet(&b);
+
+    draw_init(&b);
+
+    interface_attach(&b);
+
+    while (1) {
+        interface_interact();
+    }
+
+    return 0;
+}

src/sheet.c

@@ -0,0 +1,27 @@
+#include "sheet.h"
+#include "celltree.h"
+
+void sheet_init(struct sheet *s, size_t width, size_t height, char *title)
+{
+    s->width = width;
+    s->height = height;
+    s->root_cell = NULL;
+
+    if (title) {
+        s->title = strndup(title, MAX_STR);
+    } else {
+        s->title = strdup("");
+    }
+}
+
+void sheet_delete(struct sheet *s)
+{
+    if (s == NULL) {
+        warn("attempted to delete NULL sheet");
+        return;
+    }
+
+    celltree_delete(s->root_cell);
+    free(s->title);
+    free(s);
+}

src/sheet.h

@@ -0,0 +1,20 @@
+#ifndef SHEET_H
+#define SHEET_H
+
+#include <stddef.h>
+#include <string.h>
+#include <stdlib.h>
+#include <err.h>
+#include "config.h"
+
+struct sheet {
+    struct celltree *root_cell;
+    size_t           width;
+    size_t           height;
+    char*            title;
+};
+
+void sheet_init(struct sheet *s, size_t width, size_t height, char* title);
+void sheet_delete(struct sheet *s);
+
+#endif