aboutsummaryrefslogtreecommitdiff
path: root/budget/src/lib.rs
blob: 7d194c0e160f2248412a426f619e63968e974574 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
use std::collections::HashMap;
use std::io::ErrorKind;
use std::fs;

use toml::de::Error as DeserializerError;
use serde::{Deserialize, Deserializer};
use chrono::NaiveDate;

#[derive(Deserialize, PartialEq, Debug)]
pub struct Account {
    #[serde(deserialize_with = "deserialize_date")]
    pub start_date: NaiveDate,
    #[serde(deserialize_with = "deserialize_date")]
    pub end_date: NaiveDate,
    pub budget: f64,
    #[serde(default)]
    pub essential_categories: Vec<String>,
    pub days: Vec<Day>,
}

#[derive(Deserialize, PartialEq, Debug)]
pub struct Day {
    #[serde(deserialize_with = "deserialize_date")]
    pub date: NaiveDate,
    #[serde(default)]
    pub expenses: Vec<Expense>,
}

#[derive(Deserialize, PartialEq, Debug)]
pub struct Expense {
    pub name: String,
    pub price: f64,
    #[serde(default = "shared_qty_default")]
    pub qty: u32, // unused for now, might use it the future or remove it
    #[serde(default = "shared_qty_default")]
    pub shared: u32,
    #[serde(default = "recurring_default")]
    pub recurring: bool,
    #[serde(default)]
    pub category: Option<String>,
}

#[derive(PartialEq, Debug)]
pub struct Calculated {
    pub all_day_average: f64,
    pub essential_day_average: f64,
    pub categories_day_average: HashMap<String, f64>,
    pub essential_subtotal: f64,
    pub categories_subtotal: HashMap<String, f64>,
    pub total: f64,
    pub balance: f64,
    pub total_owed: HashMap<u32, f64>,
    pub days_left: f64,
    pub days_left_essential: f64,
    pub last_day: NaiveDate,
}

#[derive(PartialEq, Eq, Debug)]
pub enum ParseError {
    IOError(ErrorKind),
    DeserializerError(DeserializerError),
}

fn shared_qty_default() -> u32 {
    1
}

fn recurring_default() -> bool {
    false
}

// Parse the dates from toml's Datetime to Chrono's NaiveDate
fn deserialize_date<'de, D>(deserializer: D) -> Result<NaiveDate, D::Error>
where D: Deserializer<'de> {
    toml::value::Datetime::deserialize(deserializer)
        .map(|v| {
            let s = v.to_string();

            NaiveDate::parse_from_str(&s, "%Y-%m-%d")
        })?
        .map_err(serde::de::Error::custom)
}

pub fn parse_account(path: &str) -> Result<Account, ParseError> {
    let contents = match fs::read_to_string(path) {
        Ok(data) => data,
        Err(error) => {
            return Err(ParseError::IOError(error.kind()));
        },
    };

    match toml::from_str::<Account>(&contents) {
        Ok(budget) => Ok(budget),
        Err(error) => Err(ParseError::DeserializerError(error)),
    }
}

pub fn calculate(account: &Account) -> Option<Calculated> {
    if account.days.is_empty() {
        return None;
    }

    let mut calculated = Calculated {
        all_day_average: 0.0,
        essential_day_average: 0.0,
        categories_day_average: HashMap::<String, f64>::new(),
        essential_subtotal: 0.0,
        categories_subtotal: HashMap::<String, f64>::new(),
        total: 0.0,
        balance: 0.0,
        total_owed: HashMap::<u32, f64>::new(),
        days_left: 0.0,
        days_left_essential: 0.0,
        last_day: account.days.last().unwrap().date,
    };

    for day in account.days.iter() {
        if day.date > calculated.last_day {
            calculated.last_day = day.date;
        }

        for expense in day.expenses.iter() {
            calculated.total += expense.price;

            if let Some(category) = &expense.category {
                if let Some(category_subtotal) = 
                calculated.categories_subtotal.get_mut(category) {
                    *category_subtotal += expense.price;
                } else {
                    calculated.categories_subtotal.insert(
                        category.to_string(),
                        expense.price,
                    );
                }

                if account.essential_categories.contains(category) {
                    calculated.essential_subtotal += expense.price;
                }

                if expense.shared > 1 {
                    let owed = 
                        expense.price * 
                        (expense.shared as f64 - 1.0) / 
                        expense.shared as f64;

                    if let Some(total_owed_by) = 
                    calculated.total_owed.get_mut(&expense.shared) {
                        *total_owed_by += owed;
                    } else {
                        calculated.total_owed.insert(
                            expense.shared,
                            owed,
                        );
                    }
                }
            }
        }
    }

    let days_elapsed = 
        (calculated.last_day - account.start_date).num_days() + 1;

    calculated.all_day_average = calculated.total / days_elapsed as f64;
    calculated.essential_day_average = 
        calculated.essential_subtotal / days_elapsed as f64;

    for (category, subtotal) in calculated.categories_subtotal.iter() {
        calculated.categories_day_average
            .insert(
                category.clone(),
                subtotal / days_elapsed as f64,
            );
    }

    calculated.balance = account.budget - calculated.total;

    calculated.days_left = calculated.balance / calculated.all_day_average;
    calculated.days_left_essential = 
        calculated.balance / calculated.essential_day_average;

    Some(calculated)
}