//! 成本估算与预算告警服务

use sea_orm::{ColumnTrait, EntityTrait, FromQueryResult, QueryFilter, Statement};
use uuid::Uuid;

use crate::entity::ai_tenant_config;
use crate::error::AiResult;

/// 单次分析成本估算
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct CostEstimate {
    pub analysis_type: String,
    pub estimated_input_tokens: u32,
    pub estimated_output_tokens: u32,
    pub estimated_cost_usd: f64,
    pub model: String,
}

/// 预算状态
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub struct BudgetStatus {
    pub tenant_id: Uuid,
    pub monthly_budget: i64,
    pub monthly_used: i64,
    pub usage_percentage: f64,
    pub is_over_budget: bool,
    pub warning_level: BudgetWarningLevel,
}

/// 预算告警等级
#[derive(Debug, Clone, Copy, PartialEq, serde::Serialize, serde::Deserialize)]
pub enum BudgetWarningLevel {
    Normal,
    Warning,
    Critical,
    Exceeded,
}

/// 各分析类型的默认 token 估算
fn default_token_estimate(analysis_type: &str) -> (u32, u32) {
    match analysis_type {
        "lab_report" => (2000, 1500),
        "trend" => (3000, 2000),
        "checkup_plan" => (1500, 2000),
        "report_summary" => (2500, 1500),
        "dialysis_risk" => (2000, 1000),
        _ => (1500, 1000),
    }
}

/// 各模型的每百万 token 成本（USD）
fn model_cost_per_million(model: &str) -> (f64, f64) {
    // (input_cost, output_cost) per million tokens
    match model {
        m if m.contains("claude-3") => (3.0, 15.0),
        m if m.contains("claude") => (3.0, 15.0),
        m if m.contains("gpt-4") => (30.0, 60.0),
        m if m.contains("gpt-3.5") => (0.5, 1.5),
        m if m.contains("qwen") => (0.5, 1.0),
        _ => (2.0, 8.0),
    }
}

pub struct CostService {
    db: sea_orm::DatabaseConnection,
}

impl CostService {
    pub fn new(db: sea_orm::DatabaseConnection) -> Self {
        Self { db }
    }

    /// 估算单次分析成本
    pub fn estimate_cost(analysis_type: &str, model: &str) -> CostEstimate {
        let (input_tokens, output_tokens) = default_token_estimate(analysis_type);
        let (input_cost, output_cost) = model_cost_per_million(model);
        let estimated_cost_usd =
            (input_tokens as f64 * input_cost / 1_000_000.0)
                + (output_tokens as f64 * output_cost / 1_000_000.0);

        CostEstimate {
            analysis_type: analysis_type.to_string(),
            estimated_input_tokens: input_tokens,
            estimated_output_tokens: output_tokens,
            estimated_cost_usd,
            model: model.to_string(),
        }
    }

    /// 获取租户预算状态
    pub async fn get_budget_status(&self, tenant_id: Uuid) -> AiResult<BudgetStatus> {
        let config = ai_tenant_config::Entity::find()
            .filter(ai_tenant_config::Column::TenantId.eq(tenant_id))
            .filter(ai_tenant_config::Column::DeletedAt.is_null())
            .one(&self.db)
            .await?;

        let monthly_budget = config
            .as_ref()
            .map(|c| c.monthly_token_budget)
            .unwrap_or(1_000_000);

        // 查询当月已用 token
        let used = self.get_monthly_usage(tenant_id).await?;
        let usage_percentage = if monthly_budget > 0 {
            (used as f64 / monthly_budget as f64) * 100.0
        } else {
            0.0
        };

        let is_over_budget = used > monthly_budget;
        let warning_level = if is_over_budget {
            BudgetWarningLevel::Exceeded
        } else if usage_percentage >= 90.0 {
            BudgetWarningLevel::Critical
        } else if usage_percentage >= 70.0 {
            BudgetWarningLevel::Warning
        } else {
            BudgetWarningLevel::Normal
        };

        Ok(BudgetStatus {
            tenant_id,
            monthly_budget,
            monthly_used: used,
            usage_percentage,
            is_over_budget,
            warning_level,
        })
    }

    async fn get_monthly_usage(&self, tenant_id: Uuid) -> AiResult<i64> {
        #[derive(Debug, FromQueryResult)]
        struct TokenSum {
            total: Option<i64>,
        }

        let sql = r#"
            SELECT COALESCE(SUM(input_tokens + output_tokens), 0) AS total
            FROM ai_usage
            WHERE tenant_id = $1
              AND deleted_at IS NULL
              AND created_at >= DATE_TRUNC('month', CURRENT_DATE)
        "#;

        let row: Option<TokenSum> = TokenSum::find_by_statement(
            Statement::from_sql_and_values(
                sea_orm::DatabaseBackend::Postgres,
                sql,
                [tenant_id.into()],
            ),
        )
        .one(&self.db)
        .await?;

        Ok(row.and_then(|r| r.total).unwrap_or(0))
    }
}

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

    #[test]
    fn estimate_lab_report_cost() {
        let est = CostService::estimate_cost("lab_report", "claude-3-sonnet");
        assert_eq!(est.estimated_input_tokens, 2000);
        assert_eq!(est.estimated_output_tokens, 1500);
        assert!(est.estimated_cost_usd > 0.0);
    }

    #[test]
    fn estimate_trend_cost() {
        let est = CostService::estimate_cost("trend", "gpt-4");
        assert_eq!(est.estimated_input_tokens, 3000);
        assert!(est.estimated_cost_usd > 0.0);
    }

    #[test]
    fn budget_warning_levels() {
        assert_eq!(BudgetWarningLevel::Normal, BudgetWarningLevel::Normal);
        assert!(matches!(BudgetWarningLevel::Exceeded, BudgetWarningLevel::Exceeded));
    }

    #[test]
    fn usage_percentage_calculation() {
        let monthly_budget: i64 = 1_000_000;
        let monthly_used: i64 = 750_000;
        let pct = (monthly_used as f64 / monthly_budget as f64) * 100.0;
        assert!((pct - 75.0).abs() < 0.01);
    }

    #[test]
    fn over_budget_detection() {
        let monthly_budget: i64 = 100_000;
        let monthly_used: i64 = 150_000;
        assert!(monthly_used > monthly_budget);
    }

    #[test]
    fn default_unknown_type() {
        let (input, output) = default_token_estimate("unknown_type");
        assert_eq!(input, 1500);
        assert_eq!(output, 1000);
    }

    #[test]
    fn model_cost_claude() {
        let (input, output) = model_cost_per_million("claude-3-sonnet-20240229");
        assert!(input > 0.0);
        assert!(output > input);
    }
}