// email_management_system.c
// Tammy Zhong
// Implementation file for email management system functions
// (TODO)

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

#include "email_management_system.h"

// Function prototypes

// Internal functions
// Used by insertion operations
struct email *create_email(char sender[MAX_LEN], char subject[MAX_LEN], 
    double size, enum email_type type, int priority); // like create_node

// Used by `delete_email_of_priority` for commented out approach
// void delete_specific_email(struct folder *email_folder, char subject[MAX_LEN]);

// Used by `split_folder`
struct folder *insert_email_at_tail(struct folder *email_folder, char sender[MAX_LEN], 
    char subject[MAX_LEN], double size, enum email_type type, int priority);


// Function definitions

// Creates a new empty email folder 
// Similar to previous lecture code create_node
struct folder *create_folder(char name[MAX_LEN]) {
    struct folder *new_folder = malloc(sizeof(struct folder));
    strcpy(new_folder->name, name);
    new_folder->num_emails = 0;
    new_folder->emails = NULL;

    return new_folder;    
}

// Creates and initialises a new email
// Internal function used by insertion operations
// Similar to previous lecture code create_node
struct email *create_email(char sender[MAX_LEN], char subject[MAX_LEN], 
    double size, enum email_type type, int priority) {
    struct email *new_email = malloc(sizeof(struct email));
    strcpy(new_email->sender, sender);
    strcpy(new_email->subject, subject);
    new_email->size = size;
    new_email->type = type;
    new_email->priority = priority;
    new_email->next = NULL; // important

    return new_email;
}

// Add a new email to the folder at the head 
// Similar to previous lecture code insert_head
struct folder *insert_email_at_head(struct folder *email_folder, char sender[MAX_LEN], 
    char subject[MAX_LEN], double size, enum email_type type, int priority) {
    // create email
    struct email *new_email = create_email(sender, subject, size, type, priority);
    email_folder->num_emails++;

    // if there are no emails
    if (email_folder->emails == NULL) {
        email_folder->emails = new_email;
        return email_folder;
    }

    new_email->next = email_folder->emails;
    email_folder->emails = new_email;
    
    return email_folder;
}

// Prints out details of a single email 
void print_single_email(struct email *email) {

    if (email == NULL) {
        printf("Email is NULL.\n");
    }

    printf("Sender: %s\n", email->sender);
    printf("Subject: %s\n", email->subject);
    printf("Size: %lfmb\n", email->size);
    printf("Type: ");
    if (email->type == RECEIVED) {
        printf("RECEIVED\n");
    } else if (email->type == SENT) {
        printf("SENT\n");
    } else if (email->type == DRAFT) {
        printf("DRAFT\n");
    } else {
        printf("UNKNOWN\n");
    }
    printf("Priority: ");
    if (email->priority == HIGH_PRIORITY) {
        printf("HIGH_PRIORITY\n");
    } else if (email->priority == NORMAL_PRIORITY) {
        printf("NORMAL_PRIORITY\n");
    } else if (email->priority == LOW_PRIORITY) {
        printf("LOW_PRIORITY\n");
    } else {
        printf("UNKNOWN\n");
    }
}

// Print/display all emails in folder 
// Similar to previous lecture code print_list
void print_emails(struct folder *email_folder) {
    printf("Folder Name: %s\n", email_folder->name);
    struct email *current = email_folder->emails;

    if (current == NULL) {
        printf("There are no emails in this folder.\n");
    }

    while (current != NULL) {
        printf("---\n");
        print_single_email(current);
        current = current->next;
    }
}

// Returns number of emails in a given folder 
// (TODO: Improve this)
int count_emails(struct folder *email_folder) {
    // int counter = 0;
    // struct email *current = email_folder->emails;
    // while (current != NULL) {
    //     counter++;
    //     current = current->next;
    // }
    // return counter;
    return email_folder->num_emails;
}   

// Given a string, look for email where the subject is this string 
struct email *search_email(struct folder *email_folder, char subject[MAX_LEN]) {
    struct email *current = email_folder->emails;

    while (current != NULL) {
        // compare the email's subject with the given subject
        // if we find the email with the given subject
        if (strcmp(current->subject, subject) == 0) {
            return current;
        }
        current = current->next;
    }

    // cannot be found
    return NULL;
}

// Remove email(s) with certain priority (e.g. filter out low priority emails)
void delete_email_of_priority(struct folder *email_folder, int priority) {
    // Loop through the folder of emails
        // if we encounter email of given priority
            // call a function that deletes one node, 
            // delete_specific_email(folder, subject);  // loop through the list

    // only catering for when the emails we want to delete 
    // are at the head
    while (email_folder->emails != NULL && email_folder->emails->priority == priority) {
        struct email *temp = email_folder->emails;
        email_folder->emails = temp->next;
        free(temp);
        email_folder->num_emails--;
    }

    if (email_folder->emails == NULL) {
        // nothing to remove anymore
        return;
    }

    // email_folder->emails->priority != priority
    // but we still have emails in this list
    struct email *current = email_folder->emails;
    // loop through and check the next node of
    // current to see if it's one we want to delete
    while (current->next != NULL) {
        // if the next one is the one we want to delete
        if (current->next->priority == priority) {
            struct email *temp = current->next;
            current->next = temp->next; // current->next = current->next->next;
            free(temp);
            email_folder->num_emails--;
            // here we have already changed current->next
            // so it points at the element after 
            // when we try and delete
        } else {
            current = current->next;
        }

    }

}

// Append emails from folder_2 after folder_1 and returns them in the one folder
// Assumption made here assumes not same subject email in folder_1 and folder_2
struct folder *merge_folders(char merged_folder_name[MAX_LEN], 
    struct folder *folder_1, struct folder *folder_2) {
    // TODO: implement this function
    printf("merge_folders not yet implemented.\n");
    exit(1);   
}

// CHALLENGE at home for fun: Sort emails in folder based on size
// (slightly out of scope of COMP1511 - touches on sorting algorithms)
// order doesn't matter if two emails of same size
void sort_emails(struct folder *email_folder) {
    // TODO: implement this function
    printf("sort_emails not yet implemented.\n");
    exit(1);
}

// Inserts email at tail - Internal Function
// Similar to previous lecture code on insert_at_tail (no need to write this one in lecture)
struct folder *insert_email_at_tail(struct folder *email_folder, char sender[MAX_LEN], 
    char subject[MAX_LEN], double size, enum email_type type, int priority) {    
    struct email *new_email = create_email(sender, subject, size, type, priority);
	email_folder->num_emails++;
	
    // empty list case
	if (email_folder->emails == NULL) {
		email_folder->emails = new_email;
		return email_folder;
	}
    
	struct email *current = email_folder->emails;
	// loop the current pointer until the last node
	while (current->next != NULL) {
		current = current->next;
	}
	// at this pt, current->next == NULL
	// which means current is pointing at the last node
	current->next = new_email;
    
	return email_folder;
}


// Split emails in a given folder into 3 folders based on email type 
// keeping original ordering
// assumption: inbox, sent and draft are folders already malloc-ed and initialised
void split_folder(struct folder *given_folder, 
    struct folder *inbox, struct folder *sent, struct folder *draft) {
    // TODO: implement this function
    printf("split_folder not yet implemented.\n");
    exit(1);
}

// Removes all emails from a folder
// clears and delete associated memory of folder and emails in it
void clear_folder(struct folder *email_folder) {
    struct email *current = email_folder->emails;

    // loop through delete each email we encounter
    while (current != NULL) {
        struct email *temp = current;
        current = current->next;
        free(temp);
    }

    free(email_folder);

}