use aamos_core::{Currency, DecisionSource, Money, Period, TenantId};
use chrono::{DateTime, NaiveDate, Utc};
use serde::{Deserialize, Serialize};
use uuid::Uuid;

// ── Konto ─────────────────────────────────────────────────────────────────
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Account {
    pub id: Uuid,
    pub tenant_id: TenantId,
    pub account_number: String,    // t.ex. "1910", "3000"
    pub name: String,
    pub account_type: AccountType,
    pub normal_balance: BalanceSide,
    pub coa_standard: CoaStandard,
    pub parent_account: Option<String>,
    pub vat_code: Option<String>,
    pub is_active: bool,
    pub metadata: serde_json::Value,
    pub created_at: DateTime<Utc>,
    pub updated_at: DateTime<Utc>,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum AccountType {
    Asset,
    Liability,
    Equity,
    Revenue,
    Expense,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum BalanceSide {
    Debit,
    Credit,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum CoaStandard {
    BAS,
    IFRS,
    USGAAP,
    Custom,
}

// ── Verifikation ──────────────────────────────────────────────────────────
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct JournalEntry {
    pub id: Uuid,
    pub tenant_id: TenantId,
    pub entry_number: Option<i64>, // löpnummer per tenant+räkenskapsår
    pub fiscal_year: i32,
    pub period: Period,
    pub entry_date: NaiveDate,
    pub description: String,
    pub reference: Option<String>,
    pub source_type: SourceType,
    pub source_id: Option<String>,
    pub status: EntryStatus,
    pub void_reason: Option<String>,
    pub voided_at: Option<DateTime<Utc>>,
    pub voided_by: Option<String>,
    pub trace_id: Uuid,
    pub correlation_id: Uuid,
    pub user_id: String,
    pub decision_source: DecisionSource,
    pub metadata: serde_json::Value,
    pub created_at: DateTime<Utc>,
    pub posted_at: Option<DateTime<Utc>>,
    pub lines: Vec<JournalLine>,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum SourceType {
    Manual,
    ImportSie,
    ImportCsv,
    Bank,
    System,
    Agent,
    OpeningBalance,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum EntryStatus {
    Draft,
    Posted,
    Voided,
}

// ── Verifikationsrad ──────────────────────────────────────────────────────
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct JournalLine {
    pub id: Uuid,
    pub entry_id: Uuid,
    pub tenant_id: TenantId,
    pub line_number: i32,
    pub account_number: String,
    pub account_name: Option<String>,
    pub debit: Option<Money>,
    pub credit: Option<Money>,
    pub currency: Currency,
    pub amount_base: Option<Money>,
    pub vat_code: Option<String>,
    pub vat_amount: Option<Money>,
    pub cost_center: Option<String>,
    pub project_code: Option<String>,
    pub description: Option<String>,
    pub metadata: serde_json::Value,
}

// ── Period ────────────────────────────────────────────────────────────────
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LedgerPeriod {
    pub id: Uuid,
    pub tenant_id: TenantId,
    pub fiscal_year: i32,
    pub period: Period,
    pub status: PeriodStatus,
    pub opened_at: DateTime<Utc>,
    pub closed_at: Option<DateTime<Utc>>,
    pub closed_by: Option<String>,
    pub workflow_id: Option<Uuid>,
    pub trial_balance: Option<serde_json::Value>,
    pub trace_id: Uuid,
    pub metadata: serde_json::Value,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum PeriodStatus {
    Open,
    Review,
    Approved,
    Closed,
}

// ── Validering ────────────────────────────────────────────────────────────
impl JournalEntry {
    /// Validerar att verifikationen är balanserad (summa debet = summa kredit).
    pub fn is_balanced(&self) -> bool {
        let total_debit: Money = self
            .lines
            .iter()
            .filter_map(|l| l.debit)
            .fold(Money::zero(), |a, b| a + b);
        let total_credit: Money = self
            .lines
            .iter()
            .filter_map(|l| l.credit)
            .fold(Money::zero(), |a, b| a + b);
        total_debit == total_credit
    }

    /// Validerar att alla rader har antingen debet ELLER kredit (inte båda, inte inget).
    pub fn validate_lines(&self) -> Result<(), String> {
        for (i, line) in self.lines.iter().enumerate() {
            match (&line.debit, &line.credit) {
                (Some(_), Some(_)) => {
                    return Err(format!("Line {} has both debit and credit", i + 1))
                }
                (None, None) => {
                    return Err(format!("Line {} has neither debit nor credit", i + 1))
                }
                _ => {}
            }
        }
        Ok(())
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn test_tenant() -> TenantId {
        TenantId::new("test-tenant")
    }

    fn base_entry() -> JournalEntry {
        JournalEntry {
            id: Uuid::new_v4(),
            tenant_id: test_tenant(),
            entry_number: Some(1),
            fiscal_year: 2026,
            period: Period::new(2026, 1).unwrap(),
            entry_date: NaiveDate::from_ymd_opt(2026, 1, 15).unwrap(),
            description: "Test entry".to_string(),
            reference: None,
            source_type: SourceType::Manual,
            source_id: None,
            status: EntryStatus::Draft,
            void_reason: None,
            voided_at: None,
            voided_by: None,
            trace_id: Uuid::new_v4(),
            correlation_id: Uuid::new_v4(),
            user_id: "test-user".to_string(),
            decision_source: DecisionSource::User,
            metadata: serde_json::Value::Object(serde_json::Map::new()),
            created_at: Utc::now(),
            posted_at: None,
            lines: vec![],
        }
    }

    fn make_line(debit: Option<i64>, credit: Option<i64>) -> JournalLine {
        JournalLine {
            id: Uuid::new_v4(),
            entry_id: Uuid::new_v4(),
            tenant_id: test_tenant(),
            line_number: 1,
            account_number: "1910".to_string(),
            account_name: None,
            debit: debit.map(Money),
            credit: credit.map(Money),
            currency: Currency::SEK,
            amount_base: None,
            vat_code: None,
            vat_amount: None,
            cost_center: None,
            project_code: None,
            description: None,
            metadata: serde_json::Value::Object(serde_json::Map::new()),
        }
    }

    #[test]
    fn test_journal_entry_balanced() {
        let mut entry = base_entry();
        entry.lines = vec![
            make_line(Some(10000), None),   // debit 10 000
            make_line(None, Some(10000)),   // credit 10 000
        ];
        assert!(entry.is_balanced());
    }

    #[test]
    fn test_journal_entry_unbalanced() {
        let mut entry = base_entry();
        entry.lines = vec![
            make_line(Some(10000), None),   // debit 10 000
            make_line(None, Some(5000)),    // credit 5 000
        ];
        assert!(!entry.is_balanced());
    }

    #[test]
    fn test_validate_lines_ok() {
        let mut entry = base_entry();
        entry.lines = vec![
            make_line(Some(10000), None),
            make_line(None, Some(10000)),
        ];
        assert!(entry.validate_lines().is_ok());
    }

    #[test]
    fn test_validate_lines_both_debit_and_credit() {
        let mut entry = base_entry();
        entry.lines = vec![
            make_line(Some(10000), Some(10000)),
        ];
        let result = entry.validate_lines();
        assert!(result.is_err());
        assert!(result.unwrap_err().contains("both debit and credit"));
    }

    #[test]
    fn test_validate_lines_neither() {
        let mut entry = base_entry();
        entry.lines = vec![
            make_line(None, None),
        ];
        let result = entry.validate_lines();
        assert!(result.is_err());
        assert!(result.unwrap_err().contains("neither debit nor credit"));
    }

    #[test]
    fn test_period_new_valid() {
        let p = Period::new(2026, 6).unwrap();
        assert_eq!(p.year, 2026);
        assert_eq!(p.month, 6);
    }

    #[test]
    fn test_period_new_invalid_month() {
        assert!(Period::new(2026, 0).is_err());
        assert!(Period::new(2026, 13).is_err());
    }

    #[test]
    fn test_period_from_str() {
        let p = Period::from_str("2026-03").unwrap();
        assert_eq!(p.year, 2026);
        assert_eq!(p.month, 3);
    }

    #[test]
    fn test_money_operations() {
        let a = Money(1000);
        let b = Money(500);
        assert_eq!((a + b).0, 1500);
        assert_eq!((a - b).0, 500);
        assert_eq!((-a).0, -1000);
    }

    #[test]
    fn test_money_from_decimal() {
        let m = Money::from_decimal(123.45);
        assert_eq!(m.0, 12345);
    }

    #[test]
    fn test_money_to_decimal() {
        let m = Money(12345);
        assert!((m.to_decimal() - 123.45).abs() < 0.001);
    }
}