#include <arena.h>
#include <desc.h>
#include <liballoc.h>
#include <list.h>
#include <minmax.h>
#include <path.h>
#include <printf.h>
#include <process.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <str_status.h>
#include <string.h>
#include <system.h>
#include <terminal_cursor.h>

static struct arena arena;

struct strbuf {
  char* items;
  size_t count, capacity;
};

void strbuf_append (struct strbuf* strbuf, char c) {
  if (strbuf->items == NULL) {
    strbuf->capacity = 256;
    strbuf->count = 0;
    strbuf->items = arena_malloc (&arena, strbuf->capacity);
  } else {
    if (strbuf->count == strbuf->capacity) {
      size_t prev_capacity = strbuf->capacity;
      strbuf->capacity *= 2;
      strbuf->items = arena_realloc (&arena, strbuf->items, prev_capacity, strbuf->capacity);
    }
  }
  strbuf->items[strbuf->count++] = c;
}

void strbuf_append_str (struct strbuf* strbuf, const char* s) {
  while (*s)
    strbuf_append (strbuf, *s++);
}

struct context {
  struct strbuf strbuf;
};

#define CPRINTF_BUF_MAX 4096

void cprintf (struct context* context, const char* fmt, ...) {
  va_list args;
  va_start (args, fmt);

  char* buf = malloc (CPRINTF_BUF_MAX);

  if (buf == NULL) {
    va_end (args);
    return;
  }

  vsnprintf (buf, CPRINTF_BUF_MAX, fmt, args);

  va_end (args);

  strbuf_append_str (&context->strbuf, buf);
  free (buf);
}

#define LINE_BUFFER_MAX 1024
#define TOKEN_MAX       64
#define CMD_ARGS_MAX    64
#define PROMPT          "$ "

#define TOKEN_CLASS_OPAREN    0
#define TOKEN_CLASS_CPAREN    1
#define TOKEN_CLASS_WORD      2
#define TOKEN_CLASS_SEMICOLON 3
#define TOKEN_CLASS_REDIR     4

struct token {
  struct list_node_link tokens_link;
  char buffer[TOKEN_MAX];
  int class;
};

#define PREC_NONE   0
#define PREC_LOWEST 1
#define PREC_SEQ    2
#define PREC_REDIR  3

#define AST_NODE_CLASS_CMD      0
#define AST_NODE_CLASS_SUBSHELL 1
#define AST_NODE_CLASS_SEQ      2
#define AST_NODE_CLASS_REDIR    3

struct ast_node;

struct ast_cmd {
  char* name;
  char* args[CMD_ARGS_MAX];
  int arg_count;
};

struct ast_subshell {
  struct ast_node* inner;
};

struct ast_seq {
  struct ast_node* left;
  struct ast_node* right;
};

struct ast_redir {
  struct ast_node* source;
  char* file_path;
};

struct ast_node {
  int class;
  union {
    struct ast_cmd cmd;
    struct ast_subshell subshell;
    struct ast_seq seq;
    struct ast_redir redir;
  } u;
};

struct parser;

typedef struct ast_node* (*nud_func_t) (struct parser* parser, struct token* token);
typedef struct ast_node* (*led_func_t) (struct parser* parser, struct token* token,
                                        struct ast_node* left);

struct parse_rule {
  nud_func_t nud;
  led_func_t led;
  int precedence;
};

struct parser {
  struct token* current;
  struct token* next;
};

static struct ast_node* word_nud (struct parser* parser, struct token* token);

static struct ast_node* oparen_nud (struct parser* parser, struct token* token);

static struct ast_node* semicolon_led (struct parser* parser, struct token* token,
                                       struct ast_node* left);

static struct ast_node* redir_led (struct parser* parser, struct token* token,
                                   struct ast_node* left);

static struct parse_rule parse_rules[] = {
    [TOKEN_CLASS_WORD] = {&word_nud, NULL, PREC_NONE},
    [TOKEN_CLASS_OPAREN] = {&oparen_nud, NULL, PREC_NONE},
    [TOKEN_CLASS_CPAREN] = {NULL, NULL, PREC_NONE},
    [TOKEN_CLASS_SEMICOLON] = {NULL, &semicolon_led, PREC_SEQ},
    [TOKEN_CLASS_REDIR] = {NULL, &redir_led, PREC_REDIR},
};

static struct token* get_token (struct list_node_link* link) {
  if (link == NULL)
    return NULL;

  return list_entry (link, struct token, tokens_link);
}

static struct token* advance (struct parser* parser) {
  struct token* token = parser->next;

  if (token != NULL) {
    parser->current = token;
    parser->next = get_token (token->tokens_link.next);
  } else {
    parser->current = NULL;
  }

  return token;
}

static struct ast_node* parse_precedence (struct parser* parser, int precedence) {
  struct token* token = advance (parser);

  if (token == NULL)
    return NULL;

  nud_func_t nud = parse_rules[token->class].nud;

  if (nud == NULL)
    return NULL;

  struct ast_node* left = nud (parser, token);

  while (parser->next && precedence < parse_rules[parser->next->class].precedence) {
    token = advance (parser);
    led_func_t led = parse_rules[token->class].led;

    if (led != NULL)
      left = led (parser, token, left);
  }

  return left;
}

static struct ast_node* word_nud (struct parser* parser, struct token* token) {
  struct ast_node* node = arena_malloc (&arena, sizeof (*node));
  node->class = AST_NODE_CLASS_CMD;
  node->u.cmd.name = token->buffer;
  node->u.cmd.arg_count = 0;

  while (parser->next != NULL && parser->next->class == TOKEN_CLASS_WORD) {
    struct token* arg = advance (parser);

    if (node->u.cmd.arg_count < CMD_ARGS_MAX)
      node->u.cmd.args[node->u.cmd.arg_count++] = arg->buffer;
  }

  return node;
}

static struct ast_node* oparen_nud (struct parser* parser, struct token* token) {
  struct ast_node* node = arena_malloc (&arena, sizeof (*node));
  node->class = AST_NODE_CLASS_SUBSHELL;

  node->u.subshell.inner = parse_precedence (parser, PREC_LOWEST);

  if (parser->next != NULL && parser->next->class == TOKEN_CLASS_CPAREN)
    advance (parser);

  return node;
}

static struct ast_node* semicolon_led (struct parser* parser, struct token* token,
                                       struct ast_node* left) {
  struct ast_node* node = arena_malloc (&arena, sizeof (*node));
  node->class = AST_NODE_CLASS_SEQ;
  node->u.seq.left = left;
  node->u.seq.right = parse_precedence (parser, PREC_SEQ);

  return node;
}

static struct ast_node* redir_led (struct parser* parser, struct token* token,
                                   struct ast_node* left) {
  struct ast_node* node = arena_malloc (&arena, sizeof (*node));
  node->class = AST_NODE_CLASS_REDIR;
  node->u.redir.source = left;

  struct token* next_token = advance (parser);
  if (next_token != NULL && next_token->class == TOKEN_CLASS_WORD)
    node->u.redir.file_path = next_token->buffer;

  return node;
}

static int e_pid;
static int e_pgid;

static bool run = true;

static void putch (char ch) { mail_send (e_pgid, &ch, 1); }
void putchar_ (char ch) { putch (ch); }

static void tokenize (struct list_node_link** tokens, const char* text) {
  const char* p = text;

  while (*p) {
    if (isspace (*p)) {
      p++;
      continue;
    }

    if (*p == '(' || *p == ')' || *p == ';' || *p == '>') {
      struct token* token = arena_malloc (&arena, sizeof (*token));
      memset (token, 0, sizeof (*token));

      token->buffer[0] = *p;
      if (*p == '(')
        token->class = TOKEN_CLASS_OPAREN;
      else if (*p == ')')
        token->class = TOKEN_CLASS_CPAREN;
      else if (*p == ';')
        token->class = TOKEN_CLASS_SEMICOLON;
      else if (*p == '>')
        token->class = TOKEN_CLASS_REDIR;

      list_append (*tokens, &token->tokens_link);
      p++;
      continue;
    }

    if (isprint (*p)) {
      struct token* token = arena_malloc (&arena, sizeof (*token));
      memset (token, 0, sizeof (*token));
      size_t i = 0;

      while (*p && !isspace (*p) && *p != '(' && *p != ')' && *p != ';' && *p != '>') {
        if (i < TOKEN_MAX - 1)
          token->buffer[i++] = *p;
        p++;
      }

      token->class = TOKEN_CLASS_WORD;
      list_append (*tokens, &token->tokens_link);
      continue;
    }

    printf ("ERROR unknown character '%c'\n", *p);
    p++;
  }
}

static void execute (struct ast_node* root, struct context* context);

static void parse_and_execute (struct list_node_link* tokens) {
  struct parser parser;
  parser.current = NULL;
  parser.next = get_token (tokens);

  while (parser.next != NULL) {
    struct ast_node* root = parse_precedence (&parser, PREC_NONE);

    if (root != NULL) {
      struct context context = {0};
      execute (root, &context);

      if (context.strbuf.items != NULL)
        printf ("%.*s", (int)context.strbuf.count, context.strbuf.items);
    }
  }
}

static void echo (struct context* context, char** strings, size_t strings_count) {
  for (size_t i = 0; i < strings_count; i++)
    cprintf (context, "%s ", strings[i]);
}

static void mkfile (struct context* context, char** file_paths, size_t files_count) {
  char volume[VOLUME_MAX];
  const char* path;
  int ret;

  for (size_t i = 0; i < files_count; i++) {
    const char* file_path = file_paths[i];

    if (!path_parse (file_path, volume, &path)) {
      cprintf (context, "ERROR bad path '%s'\n", file_path);
      continue;
    }

    if ((ret = volume_open (volume)) < 0) {
      cprintf (context, "ERROR could not open volume '%s': %s\n", volume, str_status[-ret]);
      continue;
    }

    create_file (path);

    volume_close ();
  }
}

static void cat (struct context* context, char** file_paths, size_t files_count) {
  struct desc desc;
  char volume[VOLUME_MAX];
  const char* path;
  int ret;

  for (size_t i = 0; i < files_count; i++) {
    const char* file_path = file_paths[i];

    if (!path_parse (file_path, volume, &path)) {
      cprintf (context, "ERROR bad path '%s'\n", file_path);
      continue;
    }

    if ((ret = volume_open (volume)) < 0) {
      cprintf (context, "ERROR could not open volume '%s': %s\n", volume, str_status[-ret]);
      continue;
    }

    describe (path, &desc);

    if (desc.type != FS_FILE)
      goto close;

    char* buffer = malloc (desc.size + 1);

    if (buffer == NULL)
      goto close;

    memset (buffer, 0, desc.size + 1);
    read_file (path, 0, (uint8_t*)buffer, desc.size);
    cprintf (context, "%s\n", buffer);

  close:
    if (buffer != NULL)
      free (buffer);
    volume_close ();
  }
}

static void ls (struct context* context, const char* path_string) {
  struct desc desc;
  char volume[VOLUME_MAX];
  const char* path;
  int ret;
  struct dir_entry entry;

  if (!path_parse (path_string, volume, &path)) {
    cprintf (context, "ERROR bad path '%s'\n", path_string);
    return;
  }

  if ((ret = volume_open (volume)) < 0) {
    cprintf (context, "ERROR could not open volume '%s': %s\n", volume, str_status[-ret]);
    return;
  }

  describe (path, &desc);

  if (desc.type != FS_DIR) {
    cprintf (context, "ERROR '%s' is not a directory\n", path_string);
    volume_close ();
    return;
  }

  size_t entries = desc.size;
  cprintf (context, "total entries: %zu\n", entries);
  cprintf (context, "\n");

  for (size_t entry_num = 0; entry_num < entries; entry_num++) {
    memset (&desc, 0, sizeof (desc));
    memset (&entry, 0, sizeof (entry));

    read_dir_entry (path, &entry, entry_num);
    describe (entry.path, &desc);

    cprintf (context, "%c%-40s %-40zu\n", (desc.type == FS_DIR ? '*' : ' '), entry.path, desc.size);
  }

  volume_close ();
}

static void quit1 (struct context* context) {
  run = false;
  cprintf (context, "Goodbye!\n");
}

static void help (struct context* context) {
  cprintf (context, "Available commands:\n");
  cprintf (context, "echo <word1> <word2> <word3> ...\n");
  cprintf (context, "help\n");
  cprintf (context, "cat <file path>\n");
  cprintf (context, "ls <directory path>\n");
  cprintf (context, "mkfile <file path>\n");
  cprintf (context, "quit\n");
}

static void execute_cmd (struct ast_cmd* cmd, struct context* context) {
  if (strcmp (cmd->name, "echo") == 0) {
    echo (context, cmd->args, cmd->arg_count);
  } else if (strcmp (cmd->name, "help") == 0) {
    help (context);
  } else if (strcmp (cmd->name, "cat") == 0) {
    cat (context, cmd->args, cmd->arg_count);
  } else if (strcmp (cmd->name, "ls") == 0) {
    ls (context, cmd->args[0]);
  } else if (strcmp (cmd->name, "quit") == 0) {
    quit1 (context);
  } else if (strcmp (cmd->name, "mkfile") == 0) {
    mkfile (context, cmd->args, cmd->arg_count);
  } else {
    cprintf (context, "ERROR unknown command '%s'\n", cmd->name);
  }
}

static void execute_redir (struct ast_redir* redir, struct context* context) {
  char volume[VOLUME_MAX];
  const char* path;
  int ret;

  if (!(path_parse (redir->file_path, volume, &path))) {
    cprintf (context, "ERROR bad path '%s'\n", redir->file_path);
    return;
  }

  if ((ret = volume_open (volume)) < 0) {
    cprintf (context, "ERROR could not open volume '%s': %s\n", volume, str_status[-ret]);
    return;
  }

  create_file (path);
  write_file (path, 0, (uint8_t*)context->strbuf.items, context->strbuf.count);

  volume_close ();
}

static void execute (struct ast_node* root, struct context* context) {
  struct context subcontext = {0};

  switch (root->class) {
  case AST_NODE_CLASS_CMD:
    execute_cmd (&root->u.cmd, context);
    break;
  case AST_NODE_CLASS_SUBSHELL:
    execute (root->u.subshell.inner, &subcontext);
    break;
  case AST_NODE_CLASS_SEQ:
    execute (root->u.seq.left, context);
    execute (root->u.seq.right, context);
    break;
  case AST_NODE_CLASS_REDIR:
    execute (root->u.redir.source, &subcontext);
    execute_redir (&root->u.redir, &subcontext);
    break;
  }
}

static void exec_line (const char* line) {
  struct list_node_link* tokens = NULL;

  tokenize (&tokens, line);

  if (tokens != NULL)
    parse_and_execute (tokens);

  arena_reset (&arena);
}

void app_main (void) {
  e_pid = get_exec_pid ();
  e_pgid = get_procgroup (e_pid);

  size_t line_cursor = 0;
  char line_buffer[LINE_BUFFER_MAX + 1];
  memset (line_buffer, 0, sizeof (line_buffer));

  while (run) {
    printf (PROMPT);

    char ch = 0;
    for (;;) {
      mail_receive (&ch, 1);

      if (ch == '\n')
        break;

      if (line_cursor < LINE_BUFFER_MAX) {
        line_buffer[line_cursor++] = ch;
        printf ("%c", ch);
      }
    }

    printf ("\n");
    exec_line (line_buffer);

    line_cursor = 0;
    memset (line_buffer, 0, sizeof (line_buffer));
  }

  arena_destroy (&arena);
}