use regex::Regex;
use std::fs::File;
use std::io::BufRead;
use std::io::BufReader;
use std::io::Result;
use std::path::PathBuf;

#[derive(Debug)]
pub(crate) enum LedgerValue {
    Comment {
        value: String,
    },
    Transaction {
        date: String,
        payee: String,
        values: Vec<TransactionValue>,
    },
}

#[derive(Debug)]
pub(crate) enum TransactionValue {
    Comment {
        value: String,
    },
    Account {
        name: String,
        expression: String,
    },
}

pub(crate) fn load(path: PathBuf) -> Result<Vec<LedgerValue>> {
    const LEDGER_COMMENTS: &'static str = r#"^; (?P<comment>[[:print:]]+)\s*$"#;

    const DATE_PAYEE: &'static str = r#"(?P<date>^\d{4}/\d{2}/\d{2})(?P<payee>.*)$"#;
    const ACCOUNT_VALUE: &'static str = r#"^\s+(?P<account>[[:print:]]+)\s*(?P<expression>[[:print:]]*$)"#;
    const TRANSACTION_COMMENTS: &'static str = r#"^\s+; (?P<comment>[[:print:]]+)\s*$"#;

    let ledger_comments_reg = Regex::new(LEDGER_COMMENTS).unwrap();

    let date_payee_reg = Regex::new(DATE_PAYEE).unwrap();
    let account_value_reg = Regex::new(ACCOUNT_VALUE).unwrap();
    let transaction_comments_reg = Regex::new(TRANSACTION_COMMENTS).unwrap();

    let input = File::open(path)?;
    let buffered = BufReader::new(input);
    let lines = buffered.lines();
    let mut iter = lines.into_iter();

    let mut ledger = Vec::new();
    let mut transaction_date = String::new();
    let mut transaction_payee = String::new();
    let mut transaction_values = Vec::new();
    for line in &mut iter {
        let line = line.unwrap();
        if let Some(caps) = ledger_comments_reg.captures(&line) {
            ledger.push(LedgerValue::Comment {
                value: caps["comment"].to_string()
            });
        } else if let Some(caps) = date_payee_reg.captures(&line) {
            transaction_date = caps["date"].to_string();
            transaction_payee = caps["payee"].trim().to_string();
            break;
        }
    }
    for line in &mut iter {
        let line = line.unwrap();
        if let Some(caps) = date_payee_reg.captures(&line) {
            ledger.push(LedgerValue::Transaction {
                date: transaction_date,
                payee: transaction_payee,
                values: transaction_values,
            });
            transaction_date = caps["date"].to_string();
            transaction_payee = caps["payee"].trim().to_string();
            transaction_values = Vec::new();
        } else if let Some(caps) = transaction_comments_reg.captures(&line) {
            let value = TransactionValue::Comment {
                value: caps["comment"].to_string()
            };
            transaction_values.push(value);
        } else if let Some(caps) = account_value_reg.captures(&line) {
            let value = TransactionValue::Account {
                name: caps["account"].to_string(),
                expression: caps["expression"].to_string(),
            };
            transaction_values.push(value);
        }
    }

    ledger.push(LedgerValue::Transaction {
        date: transaction_date,
        payee: transaction_payee,
        values: transaction_values,
    });

    Ok(ledger)
}