#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>

#include "utils.h"
#include "exec.h"
#include "preproc.h"


char* get_var(char* varname, ShellState* shstate) {
    MaybeStr maybe_varval = get_map_value(&shstate->shell_vars, varname); 
    if (maybe_varval.some == true) return maybe_varval.value;
    return getenv(varname);
}

typedef struct {
    QuotationMode qmode;  
    char* content;
} ExpandedChunk;


ExpandedChunk expand_chunk(Chunk chunk, ShellState* shstate) {
    char* content;
    if (chunk.qmode == SINGLE_Q || chunk.kind == LITERAL) {
        if (chunk.qmode == SINGLE_Q && chunk.kind != LITERAL) exit(69);
        content = chunk.as.literal_str;
    } else if (chunk.kind == VAR_EXP) {
        content = get_var(chunk.as.varname, shstate);
    } else if (chunk.kind == REGION_EXP) {
        exit(7); // Not supported yet; arithm
    }
    return (ExpandedChunk){.qmode = chunk.qmode, .content = content};
}


typedef struct {
    StrVec complete_strs;
    String active_str;
} WordSplittingGerm;

void add_expchunk(char* next_str, WordSplittingGerm* curr_res) {
     for (int pos = 0; pos < strlen(next_str); pos++) {
        if (next_str[pos] == ' ') {
            push_to_StrVec(&curr_res->complete_strs, inner(&curr_res->active_str));
            curr_res->active_str = make_String(256);
        } else {
            push_to_String(&curr_res->active_str, next_str[pos]);
        }
    }
}

StrVec expand_word(Word word, ShellState* state) {
    WordSplittingGerm curr_res = {.complete_strs = make_StrVec(256), .active_str = make_String(25)};
    for (int i = 0; i < word.count; i++) {
        Chunk curr_cunk = **get_from_Word(&word, i);
        ExpandedChunk curr_exp = expand_chunk(curr_cunk, state);
        switch (curr_exp.qmode) {
            case UN_Q:
                add_expchunk(curr_exp.content, &curr_res);
                break;
            case SINGLE_Q:
                append_str_to_String(&curr_res.active_str, curr_exp.content);
                break;
            case DOUBLE_Q:
                append_str_to_String(&curr_res.active_str, curr_exp.content);
        }
    }

    if (curr_res.active_str.count > 0) {
        push_to_StrVec(&curr_res.complete_strs, inner(&curr_res.active_str));
    }

    return curr_res.complete_strs;
}


void merge_strvecs(StrVec* target, StrVec* source) {
    for (int i = 0; i < source->count; i++) {
        push_to_StrVec(target, *get_from_StrVec(source, i));
    }
}


char** make_cmd_args(Command command, ShellState* shstate) {
    StrVec arg_str_vec = make_StrVec(256);
    for (int i = 0; i < command.args.count; i++) {
        Token arg_i = *get_from_TokenVec(&command.args, i);
        StrVec expanded_i;
        switch (arg_i.kind) {
            case TOK_WORD:
                expanded_i = expand_word(arg_i.as.word, shstate);
                merge_strvecs(&arg_str_vec, &expanded_i);
                break;
            default:
                exit(67);
        }
    }
    int argcount = arg_str_vec.count;
    char** arg_str_arr = malloc(sizeof(char*) * (argcount + 1));
    for (int j = 0; j < argcount; j++) {
        arg_str_arr[j] = *get_from_StrVec(&arg_str_vec, j);
    }
    arg_str_arr[argcount] = NULL;
    return arg_str_arr;
}


typedef struct {
    char** args;
    int stdin_fd;
    int stdout_fd;
    IntVec child_close_fds;
    IntVec parent_close_fds;
} ExecutableCommand;


void execute_command(ExecutableCommand cmd, int* pgid) {
    pid_t pid = fork();
    
    if (pid == 0) {
        if (*pgid == -1) {
            setpgid(0, 0);
        } else {
            setpgid(0, *pgid);
        }
        
        dup2(cmd.stdin_fd, STDIN_FILENO);
        dup2(cmd.stdout_fd, STDOUT_FILENO);

        for (int i = 0; i < cmd.child_close_fds.count; i++) {
            close(*get_from_IntVec(&cmd.child_close_fds, i));
        }

        signal(SIGINT,  SIG_DFL);
        signal(SIGQUIT, SIG_DFL);
        signal(SIGTSTP, SIG_DFL);
        signal(SIGTTIN, SIG_DFL);
        signal(SIGTTOU, SIG_DFL);

        execvp(cmd.args[0], cmd.args);
        exit(67);
    }

    if (*pgid == -1) {
        setpgid(pid, pid);
        *pgid = pid;
    } else {
        setpgid(pid, *pgid);
    }
}




void run_pipeline(Pipeline pl, ShellState* shstate) {
    signal(SIGTTIN, SIG_IGN);
    signal(SIGTTOU, SIG_IGN);

    int last_pipe_fd;
    int pgid = -1;
    for (int i = 0; i < pl.count; i++) {
        PipelineElement elem = *get_from_Pipeline(&pl, i);

        ExecutableCommand cmd = {.child_close_fds = make_IntVec(64), .parent_close_fds = make_IntVec(64)};
        cmd.args = make_cmd_args(elem.cmd, shstate);

        if (i == 0) {
            cmd.stdin_fd = STDIN_FILENO;
        } else {
            cmd.stdin_fd = last_pipe_fd;
            push_to_IntVec(&cmd.child_close_fds, last_pipe_fd);
            push_to_IntVec(&cmd.parent_close_fds, last_pipe_fd);
        }

        if (elem.conn == CONN_PIPE) {
            int pipe_fds[2];
            pipe(pipe_fds);
            cmd.stdout_fd = pipe_fds[1];
            push_to_IntVec(&cmd.child_close_fds, pipe_fds[1]);
            push_to_IntVec(&cmd.parent_close_fds, pipe_fds[1]);
            last_pipe_fd = pipe_fds[0];
        } else {
            cmd.stdout_fd = STDOUT_FILENO;
        }

        execute_command(cmd, &pgid);
        
        for (int j = 0; j < cmd.parent_close_fds.count; j++) {
            close(*get_from_IntVec(&cmd.parent_close_fds, j));
        }
    }
    tcsetpgrp(STDIN_FILENO, pgid); 
    while (waitpid(-pgid, NULL, 0) > 0); 
    tcsetpgrp(STDIN_FILENO, getpgrp());
}