#include "../command.h"
#include "../util//regex.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define INPUT_LEN 1024

static char** lines = NULL;
static unsigned long line_capacity;
static unsigned long line_count;
static unsigned long line_current;
static bool pending_writes;

enum LineAddressType {
    INDEX,
    RANGE,
    SET,
};

struct LineAddress {
    enum LineAddressType type;
    union {
        struct {
            long int i;
        } index;
        struct {
            long int a;
            long int b;
        } range;
        struct {
            long int* b;
            unsigned long c;
            unsigned long s;
        } set;
    } data;
    bool empty;
};

enum RegexDirection {
    BEFORE,
    AFTER,
    ALL
};

static bool parse_regex(char** end, struct LineAddress* address, enum RegexDirection dir) {
    char c;
    char* index = *end;
    char* regex_str = index;
    while(true) {
        c = *(index++);
        if (c == '\0') {
            fprintf(stderr, "error: missing regex after %c\n", dir == BEFORE ? '?' : '/');
            return false;
        }
        if (c == (dir == BEFORE ? '?' : '/')) {
            *(index - 1) = '\0';
            break;
        }
    }
    unsigned long cap = 8;
    unsigned long siz = 0;
    long int* buf = malloc(cap * sizeof(unsigned long));

    re_t regex = re_compile(regex_str);
    unsigned long i = (dir == ALL ? 0 : line_current);
    unsigned long until = (dir == BEFORE ? 0 : line_count - 1);
    for (; (dir == BEFORE ? i >= until : i < until); dir == BEFORE ? i-- : i++) {
        int len;
        if (re_matchp(regex, lines[i], &len) == -1) {
            if (dir == BEFORE && i == 0) break;
            continue;
        }
        if (cap == siz) {
            cap *= 2;
            buf = realloc(buf, cap * sizeof(unsigned long));
        }
        buf[siz] = i;
        siz++;
        if (dir == BEFORE && i == 0) break;
    }

    address->type = SET;
    address->data.set.s = siz;
    address->data.set.c = cap;
    address->data.set.b = buf;
    *end = index;
    return true;
}

static bool read_address(char** command, bool whitespace, struct LineAddress* a) {
    char* index = *command;
    struct LineAddress address;
    memset(&address, 0, sizeof(struct LineAddress));
    
    address.empty = false;
    if (strlen(*command) < 1) {
        address.type = INDEX;
        address.data.index.i = line_current + 1;
        if (line_current >= line_count) line_current = line_count - 1;
        *a = address;
        return true;
    }

    char* end_pre;
    long int n_pre = strtol(index, &end_pre, 10) - 1;
    if (end_pre == index) {
        n_pre = -1;
    } else {
        if (n_pre < 0) {
            fprintf(stderr, "error: input cannot be negative\n");
            return false;
        }
        index = end_pre;
    }
    
    char pre = *(index++);
    switch (pre) {
        case '.':
            address.type = INDEX;
            address.data.index.i = line_current;
            break;
        case '$':
            address.type = INDEX;
            address.data.index.i = line_count - 1;
            break;
        case '-':
        case '^': {
            address.type = INDEX;
            char* end;
            long int n = strtol(index, &end, 10) - 1;
            if (n < 0) {
                fprintf(stderr, "error: input cannot be negative\n");
                return false;
            }
            if (index == end) {
                address.data.index.i = line_current - 1;
            } else {
                address.data.index.i = line_current - n;
            }
            if (address.data.index.i < 0) {
                fprintf(stderr, "error: line number %ld does not exist\n", address.data.index.i + 1);
                return false;
            }
            break;
        }
        case '+': {
            address.type = INDEX;
            char* end;
            long int n = strtol(index, &end, 10) - 1;
            if (n < 0) {
                fprintf(stderr, "error: input cannot be negative\n");
                return false;
            }
            if (index == end) {
                address.data.index.i = line_current + 1;
            } else {
                address.data.index.i = line_current + n;
            }
            if (address.data.index.i >= (long int) line_count) {
                fprintf(stderr, "error: line number %ld does not exist\n", address.data.index.i + 1);
                return false;
            }
            break;
        }
        case '%':
            address.type = RANGE;
            address.data.range.a = 0;
            address.data.range.b = line_count - 1;
            break;
        case ';':
            address.type = RANGE;
            address.data.range.a = line_current;
            address.data.range.b = line_count - 1;
            break;
        case '/': 
            if (!parse_regex(&index, &address, AFTER)) return false;
            break;
        case '?':
            if (!parse_regex(&index, &address, BEFORE)) return false;
            break;
        default: {
            index--;
            if (n_pre == -1) {
                address.type = INDEX;
                address.data.index.i = line_current;
                address.empty = true;
                break;
            } else if (whitespace) {
                address.type = INDEX;
                address.data.index.i = line_current + n_pre;
            } else {
                address.type = INDEX;
                address.data.index.i = n_pre;
            }
            if (address.data.index.i < 0 || address.data.index.i >= (long int) line_count) {
                fprintf(stderr, "error: line number %ld does not exist\n", address.data.index.i + 1);
                return false;
            }
        }
    }
    *command = index;
    *a = address;
    return true;
}

static void free_address (struct LineAddress address) {
    if (address.type != SET) return;
    free(address.data.set.b);
}

static void free_data() {
    if (lines == NULL) return;
    for (unsigned long i = 0; i < line_count; i++) 
        free(lines[i]);
    free(lines);
    lines = NULL;
}

static void load_empty() {
    free_data();

    line_capacity = 8;
    lines = malloc(sizeof(char*) * line_capacity);

    line_count = 0;
    line_current = 0;
    pending_writes = false;
}

static void get_input(FILE* file, char*** buffer, unsigned long* capacity, unsigned long* size) {
    unsigned long cap = 8;
    unsigned long siz = 0;
    char** buf = malloc(sizeof(char*) * cap);

    char* line = NULL;
    size_t offset = 0;
    
    clearerr(stdin);
    while (getline(&line, &offset, file) != -1) {
        if (cap == siz) {
            cap *= 2;
            buf = realloc(buf, sizeof(char*) * cap);
        }
        buf[siz] = line;
        siz++;
        line = NULL;
    }

    free(line);

    *buffer = buf;
    *capacity = cap;
    *size = siz;
}

int ed_getline(char *buf, size_t size) {
    size_t i = 0;
    int ch;
    clearerr(stdin);
    while ((ch = getchar()) != EOF) {  // Read until EOF ...
        if (i + 1 < size) {
            buf[i++] = ch;
        }
        if (ch == '\n') {  // ... or end of line
            break;  
        }
    } 
    buf[i] = '\0';
    if (i == 0) { 
        return EOF;
    }
    return i;
}

static void load_file(FILE* file) {
    free_data();
    line_current = 0;
    get_input(file, &lines, &line_capacity, &line_count);
    if (file != stdin)
        fclose(file);
}

static bool check_if_sure() {
    if (!pending_writes) {
        return true;
    }

    printf("Do you really want to quit? ");
    fflush(stdout);

    char buf[INPUT_LEN];
    if (ed_getline(buf, INPUT_LEN) == EOF) {
        putchar('\n');
        return false;
    }

    return prefix("y", buf);
}

static bool skip_whitespace(char** index) {
    char c;
    bool w = false;
    while (c = **index, c == ' ' || c == '\t') { (*index)++; w = true; }
    return w;
}

static void expand(unsigned long count) {
    if (count < line_capacity) return;
    line_capacity *= 2;
    if (count > line_capacity) line_capacity = count;
    lines = realloc(lines, line_capacity * sizeof(char*));
}

static void append_lines(unsigned long index, char** new, unsigned long new_len) {
    if (new_len < 1) return;
    pending_writes = true;
    expand(line_count + new_len);
    if (index + 1 <= line_count)
        memmove(&lines[index+new_len], &lines[index], sizeof(char*) * (line_count - index));
    memcpy(&lines[index], new, sizeof(char*) * new_len);
    line_count += new_len;
}

static void delete_lines(unsigned long a, unsigned long b) {
    if (b < a) return;
    pending_writes = true;
    for (unsigned long i = a; i <= b; i++) {
        free(lines[i]);
    }
    if (b == line_count - 1) {
        line_count = a;
        return;
    }
    memmove(&lines[a], &lines[b+1], sizeof(char*) * (line_count - (b + 1)));
    line_count -= (b - a) + 1;
    line_current = a;
    if (line_current >= line_count) line_current = line_count - 1;
}

static bool handle_append(struct LineAddress* address) {
    if (address->type != INDEX) {
        fprintf(stderr, "error: append command requires index addressing\n");
        return false;
    }
    if (line_count == 0) {
        address->data.index.i = -1;
    }
    char** buf;
    unsigned long cap, size;
    get_input(stdin, &buf, &cap, &size);
    if (size > 0) {
        append_lines(address->data.index.i + 1, buf, size);
    }
    line_current += size;
    free(buf);
    return true;
}

static bool handle_delete(struct LineAddress* address) {
    if (address->empty && address->data.index.i >= (long int) line_count) {
        fprintf(stderr, "error: line number %ld does not exist\n", address->data.index.i + 1);
        return false;
    }
    if (address->type == INDEX) {
        delete_lines(address->data.index.i, address->data.index.i);
    } else if (address->type == RANGE) {
        delete_lines(address->data.range.a, address->data.range.b);
    } else if (address->type == SET) {
        for (unsigned long i = 0; i < address->data.set.s; i++) {
            delete_lines(address->data.set.b[i], address->data.set.b[i]);
        }
    }
    return true;
}

static void prompt() {
    printf("%ld: ", line_current + 1);
    fflush(stdout);

    char buf[INPUT_LEN];
    if (ed_getline(buf, INPUT_LEN) == EOF) { putchar('\n'); return; }
    if (buf[0] == '\0') { putchar('\n'); return; }

    char* index = &buf[0];
    bool whitespace = skip_whitespace(&index);

    struct LineAddress address;
    if (!read_address(&index, whitespace, &address)) return;

    char cmd = *(index++);
    
    if (cmd == ',') {
        if (address.type != INDEX) {
            fprintf(stderr, "error: comma range addressing requires two index addresses\n");
            free_address(address);
            return;
        }
        struct LineAddress address2;
        whitespace = skip_whitespace(&index);
        if (!read_address(&index, whitespace, &address2)) {
            free_address(address);
            return;
        }
        if (address2.type != INDEX) {
            fprintf(stderr, "error: comma range addressing requires two index addresses\n");
            free_address(address);
            free_address(address2);
            return;
        }
        address.type = RANGE;
        address.data.range.a = address.data.index.i; // cursed
        address.data.range.b = address2.data.index.i;

        cmd = *(index++);
    }

    if (address.type == RANGE && address.data.range.a > address.data.range.b) {
        fprintf(stderr, "error: range addressing must be in ascending order\n");
        free_address(address);
        return;
    }

    switch (cmd) {
        case '\n':
        case '\0':
            if (address.empty) {
                if (line_current == line_count) {
                    fprintf(stderr, "error: line number %ld does not exist\n", line_current + 1);
                    break;
                } else if (line_current + 1 == line_count) {
                    fprintf(stderr, "error: line number %ld does not exist\n", line_current + 2);
                    break;
                } else {
                    line_current++;
                }
                printf("%s", lines[line_current]);
                break;
            }
            if (address.type == INDEX) {
                line_current = address.data.index.i;
            } else if (address.type == RANGE) {
                line_current = address.data.range.b;
            } else if (address.type == SET) {
                fprintf(stderr, "error: unexpected range addressing\n");
                break;
            }
            printf("%s", lines[line_current]);
            break;
        case 'a':
            handle_append(&address);
            break;
        case 'd':
            handle_delete(&address);
            break;
        case 'c':
            if (!handle_delete(&address)) { break; }
            address.type = INDEX;
            address.data.index.i = line_current - 1;
            handle_append(&address);
            break;
        case 'p':
            if (address.empty && address.data.index.i >= (long int) line_count) {
                fprintf(stderr, "error: line number %ld does not exist\n", address.data.index.i + 1);
                break;
            }
            if (address.type == INDEX) {
                printf("%s", lines[address.data.index.i]);
            } else if (address.type == RANGE) {
                for (long int i = address.data.range.a; i <= address.data.range.b; i++) {
                    printf("%s", lines[i]);
                }
            } else if (address.type == SET) {
                for (unsigned long i = 0; i < address.data.set.s; i++) {
                    printf("%s", lines[address.data.set.b[i]]);
                }
            }
            break;
        case 'q':
            if(check_if_sure()) {
                free_address(address);
                free_data();
                exit(EXIT_SUCCESS);
            };
            break;
        case 'Q':
            free_address(address);
            free_data();
            exit(EXIT_SUCCESS);
        case 'g':
            skip_whitespace(&index);
            free_address(address);
            if (*(index++) != '/') {
                fprintf(stderr, "error: unexpected character at start or regex\n");
                break;
            }
            if (!parse_regex(&index, &address, ALL)) { return; }
            for (unsigned long i = 0; i < address.data.set.s; i++) {
                printf("%s", lines[address.data.set.b[i]]);
            }
            break;
        default:
            fprintf(stderr, "error: unimplemented command\n");
            break;
    }

    free_address(address);

}

static void prompt_loop() {
    while (true) {
        prompt();
    }
}

COMMAND(ed) {
    if (argc < 1) {
        load_empty();
        prompt_loop();
    } else {
        FILE* file = get_file(argv[0], "r");
        load_file(file);
        prompt_loop();
    }
    return EXIT_SUCCESS;
}