rustminidb 0.1.0

//! SQL 解析器
//!
//! 基于 sqlparser-rs crate，将其 AST 转换为 RustMinidb 内部表示。
//! MVP 支持：CREATE TABLE, INSERT, SELECT, UPDATE, DELETE, DROP TABLE。

use sqlparser::ast::{
    ColumnDef as SqlColumnDef, ColumnOption, DataType, Expr, ObjectType, Query, SelectItem,
    SetExpr, Statement, TableWithJoins, Value as SqlValue, Ident,
};
use sqlparser::dialect::GenericDialect;
use sqlparser::parser::Parser as SqlParserParser;

use crate::error::{ParseError, Result};
use crate::sql::types::{ColumnDef, ColumnType, Value};

/// RustMinidb 支持的 SQL 语句类型（MVP）
#[derive(Debug, Clone)]
pub enum SqlStatement {
    CreateTable {
        name: String,
        columns: Vec<ColumnDef>,
        if_not_exists: bool,
    },
    Insert {
        table: String,
        columns: Vec<String>,
        values: Vec<Vec<Value>>,
    },
    Select {
        table: String,
        columns: Vec<String>,
        where_clause: Option<WhereClause>,
        order_by: Option<OrderBy>,
        limit: Option<usize>,
        offset: Option<usize>,
    },
    Update {
        table: String,
        assignments: Vec<(String, Value)>,
        where_clause: Option<WhereClause>,
    },
    Delete {
        table: String,
        where_clause: Option<WhereClause>,
    },
    DropTable {
        name: String,
    },
}

/// WHERE 条件
#[derive(Debug, Clone)]
pub enum WhereClause {
    Simple {
        column: String,
        operator: ComparisonOp,
        value: Value,
    },
    And(Box<WhereClause>, Box<WhereClause>),
    Or(Box<WhereClause>, Box<WhereClause>),
}

/// 比较操作符
#[derive(Debug, Clone)]
pub enum ComparisonOp {
    Eq,    // =
    NotEq, // <>
    Lt,    // <
    LtEq,  // <=
    Gt,    // >
    GtEq,  // >=
}

/// 排序规则
#[derive(Debug, Clone)]
pub struct OrderBy {
    pub column: String,
    pub ascending: bool,
}

/// SQL 解析器
pub struct SqlParser;

impl SqlParser {
    /// 解析 SQL 文本为内部语句
    pub fn parse(sql: &str) -> Result<SqlStatement> {
        let dialect = GenericDialect {};
        let statements = SqlParserParser::parse_sql(&dialect, sql)
            .map_err(|e| ParseError::Syntax(e.to_string()))?;

        if statements.is_empty() {
            return Err(ParseError::Empty.into());
        }

        if statements.len() > 1 {
            return Err(ParseError::MultipleStatements("MVP 只支持单条语句".to_string()).into());
        }

        Self::convert_statement(&statements[0])
    }

    /// 将 sqlparser AST 转换为内部表示
    fn convert_statement(stmt: &Statement) -> Result<SqlStatement> {
        match stmt {
            Statement::CreateTable(create) => {
                Self::convert_create_table(&create.name, &create.columns, create.if_not_exists)
            }
            Statement::Insert(insert) => {
                let table_name = &insert.table;
                let columns = &insert.columns;
                let source = &insert.source;
                Self::convert_insert(table_name, columns, source)
            }
            Statement::Query(query) => Self::convert_select(query),
            Statement::Update {
                table,
                assignments,
                selection,
                ..
            } => Self::convert_update(table, assignments, selection.as_ref()),
            Statement::Delete(delete) => {
                let table_name = if !delete.tables.is_empty() {
                    Self::object_name_to_string(&delete.tables[0])
                } else {
                    // 从 from 字段提取表名
                    Self::from_table_to_string(&delete.from)
                };
                Self::convert_delete(&table_name, delete.selection.as_ref())
            }
            Statement::Drop {
                object_type,
                names,
                ..
            } => Self::convert_drop(*object_type, names),
            _ => Err(ParseError::Unsupported(format!(
                "不支持的 SQL 语句: {:?}",
                stmt
            ))
            .into()),
        }
    }

    fn convert_create_table(
        name: &sqlparser::ast::ObjectName,
        columns: &[SqlColumnDef],
        if_not_exists: bool,
    ) -> Result<SqlStatement> {
        let table_name = Self::object_name_to_string(name);
        let mut cols = Vec::new();

        for col in columns {
            let col_type = Self::convert_data_type(&col.data_type)?;
            let mut nullable = true;
            let mut is_primary_key = false;
            let mut default = None;
            let mut comment = None;

            for opt in &col.options {
                match &opt.option {
                    ColumnOption::NotNull => nullable = false,
                    ColumnOption::Unique { is_primary: true, .. }
                    | ColumnOption::Unique { is_primary: false, .. } => {}
                    ColumnOption::Default(expr) => {
                        default = Some(Self::expr_to_value(expr)?);
                    }
                    ColumnOption::Comment(s) => {
                        comment = Some(s.clone());
                    }
                    _ => {}
                }
            }

            // 处理列约束中的 PRIMARY KEY
            for opt in &col.options {
                if let ColumnOption::Unique { is_primary: true, .. } = &opt.option {
                    is_primary_key = true;
                    nullable = false;
                }
            }

            cols.push(ColumnDef {
                name: col.name.to_string(),
                col_type,
                nullable,
                is_primary_key,
                default,
                comment,
            });
        }

        // 如果没有明确的 PRIMARY KEY，尝试找第一个 "INT PRIMARY KEY" 或 "id" 列
        if !cols.iter().any(|c| c.is_primary_key) {
            // 检查是否有列名包含 "id" 且类型为 Integer
            if let Some(id_col) = cols.iter_mut().find(|c| c.name.to_lowercase() == "id") {
                id_col.is_primary_key = true;
                id_col.nullable = false;
            }
        }

        Ok(SqlStatement::CreateTable {
            name: table_name,
            columns: cols,
            if_not_exists,
        })
    }

    fn convert_insert(
        table_name: &sqlparser::ast::TableObject,
        columns: &[Ident],
        source: &Option<Box<Query>>,
    ) -> Result<SqlStatement> {
        let table = Self::table_object_to_string(table_name);
        let cols: Vec<String> = columns.iter().map(|c| c.to_string()).collect();

        let values = match source {
            Some(query) => {
                match &*query.body {
                    SetExpr::Values(values) => {
                        let mut rows = Vec::new();
                        for row in &values.rows {
                            let mut row_values = Vec::new();
                            for expr in row {
                                row_values.push(Self::expr_to_value(expr)?);
                            }
                            rows.push(row_values);
                        }
                        rows
                    }
                    _ => return Err(ParseError::Unsupported("MVP 只支持 VALUES 插入".to_string()).into()),
                }
            }
            None => return Err(ParseError::Unsupported("MVP 需要 VALUES 子句".to_string()).into()),
        };

        Ok(SqlStatement::Insert {
            table,
            columns: cols,
            values,
        })
    }

    fn convert_select(query: &Query) -> Result<SqlStatement> {
        let body = &query.body;
        let select = match &**body {
            SetExpr::Select(s) => s,
            _ => {
                return Err(
                    ParseError::Unsupported("不支持的查询类型".to_string()).into(),
                )
            }
        };

        // 提取表名（只支持单表）
        let table = match select.from.first() {
            Some(TableWithJoins {
                relation, joins, ..
            }) if joins.is_empty() => Self::table_factor_to_string(relation),
            Some(_) => {
                return Err(
                    ParseError::Unsupported("MVP 不支持 JOIN".to_string()).into(),
                )
            }
            None => return Err(ParseError::Syntax("缺少 FROM 子句".to_string()).into()),
        };

        // 提取列
        let columns = {
            let mut cols = Vec::new();
            for item in &select.projection {
                match item {
                    SelectItem::UnnamedExpr(Expr::Identifier(id)) => {
                        cols.push(id.to_string());
                    }
                    SelectItem::ExprWithAlias { expr: _, alias } => {
                        cols.push(alias.to_string());
                    }
                    SelectItem::Wildcard { .. } => {
                        cols.push("*".to_string());
                    }
                    SelectItem::QualifiedWildcard(_, _) => {
                        cols.push("*".to_string());
                    }
                    _ => {
                        return Err(ParseError::Unsupported(format!(
                            "不支持的 SELECT 项: {:?}",
                            item
                        ))
                        .into())
                    }
                }
            }
            cols
        };

        // 提取 WHERE
        let where_clause = select
            .selection
            .as_ref()
            .map(|expr| Self::convert_expr_to_where(expr))
            .transpose()?;

        // 提取 ORDER BY
        let order_by = query.order_by.as_ref().and_then(|ob| {
            if ob.exprs.is_empty() {
                None
            } else {
                let first = &ob.exprs[0];
                let column = match &first.expr {
                    Expr::Identifier(id) => id.to_string(),
                    _ => return None,
                };
                Some(OrderBy {
                    column,
                    ascending: first.asc.unwrap_or(true),
                })
            }
        });

        // 提取 LIMIT / OFFSET
        let limit = query.limit.as_ref().and_then(|l| match l {
            Expr::Value(SqlValue::Number(n, _)) => n.parse::<usize>().ok(),
            _ => None,
        });

        let offset = query.offset.as_ref().and_then(|o| match &o.value {
            Expr::Value(SqlValue::Number(n, _)) => n.parse::<usize>().ok(),
            _ => None,
        });

        Ok(SqlStatement::Select {
            table,
            columns,
            where_clause,
            order_by,
            limit,
            offset,
        })
    }

    fn convert_update(
        table: &TableWithJoins,
        assignments: &[sqlparser::ast::Assignment],
        selection: Option<&Expr>,
    ) -> Result<SqlStatement> {
        let table = Self::table_factor_to_string(&table.relation);

        let mut assigns = Vec::new();
        for assignment in assignments {
            let col = assignment.target.to_string();
            let val = Self::expr_to_value(&assignment.value)?;
            assigns.push((col, val));
        }

        let where_clause = selection
            .map(|expr| Self::convert_expr_to_where(expr))
            .transpose()?;

        Ok(SqlStatement::Update {
            table,
            assignments: assigns,
            where_clause,
        })
    }

    fn convert_delete(
        table_name: &str,
        selection: Option<&Expr>,
    ) -> Result<SqlStatement> {
        let where_clause = selection
            .map(|expr| Self::convert_expr_to_where(expr))
            .transpose()?;

        Ok(SqlStatement::Delete {
            table: table_name.to_string(),
            where_clause,
        })
    }

    #[allow(unreachable_code)]
    fn convert_drop(object_type: ObjectType, names: &[sqlparser::ast::ObjectName]) -> Result<SqlStatement> {
        if matches!(object_type, ObjectType::Table) {
            if names.is_empty() {
                return Err(ParseError::Syntax("缺少表名".to_string()).into());
            }
            let name = Self::object_name_to_string(&names[0]);
            Ok(SqlStatement::DropTable { name })
        } else {
            Err(ParseError::Unsupported("只支持 DROP TABLE".to_string()).into())
        }
    }

    // ── 辅助方法 ──

    fn convert_data_type(dt: &DataType) -> Result<ColumnType> {
        match dt {
            DataType::Int(_) | DataType::Integer(_) | DataType::BigInt(_) => {
                Ok(ColumnType::Integer)
            }
            DataType::Float(_) | DataType::Double(_) | DataType::Real => Ok(ColumnType::Float),
            DataType::Text | DataType::String(_) | DataType::Char(_) | DataType::Varchar(_) => {
                Ok(ColumnType::Text)
            }
            DataType::Boolean => Ok(ColumnType::Boolean),
            DataType::Timestamp(_, _) => {
                Ok(ColumnType::Timestamp)
            }
            DataType::Blob(_) | DataType::Bytes(_) => Ok(ColumnType::Blob),
            _ => {
                // 默认转为 Text
                Ok(ColumnType::Text)
            }
        }
    }

    fn expr_to_value(expr: &Expr) -> Result<Value> {
        match expr {
            Expr::Value(SqlValue::Number(n, _)) => {
                // 尝试解析为整数，失败则解析为浮点数
                if let Ok(v) = n.parse::<i64>() {
                    Ok(Value::Integer(v))
                } else if let Ok(v) = n.parse::<f64>() {
                    Ok(Value::Float(v))
                } else {
                    Ok(Value::Text(n.clone()))
                }
            }
            Expr::Value(SqlValue::SingleQuotedString(s)) => Ok(Value::Text(s.clone())),
            Expr::Value(SqlValue::Boolean(b)) => Ok(Value::Boolean(*b)),
            Expr::Value(SqlValue::Null) => Ok(Value::Null),
            Expr::UnaryOp { op: _, expr } => {
                // 处理负数
                if let Expr::Value(SqlValue::Number(n, _)) = expr.as_ref() {
                    if let Ok(v) = n.parse::<i64>() {
                        return Ok(Value::Integer(-v));
                    } else if let Ok(v) = n.parse::<f64>() {
                        return Ok(Value::Float(-v));
                    }
                }
                Self::expr_to_value(expr)
            }
            Expr::TypedString { data_type: _, value } => {
                Ok(Value::Text(value.clone()))
            }
            Expr::CompoundIdentifier(parts) => {
                Ok(Value::Text(parts.iter().map(|p| p.to_string()).collect::<Vec<_>>().join(".")))
            }
            Expr::Identifier(id) => Ok(Value::Text(id.to_string())),
            _ => Err(ParseError::Syntax(format!("不支持的表达式: {:?}", expr)).into()),
        }
    }

    fn convert_expr_to_where(expr: &Expr) -> Result<WhereClause> {
        match expr {
            Expr::BinaryOp {
                left,
                op,
                right,
            } => {
                let op_str = op.to_string();
                let operator = match op_str.as_str() {
                    "=" => ComparisonOp::Eq,
                    "<>" | "!=" => ComparisonOp::NotEq,
                    "<" => ComparisonOp::Lt,
                    "<=" => ComparisonOp::LtEq,
                    ">" => ComparisonOp::Gt,
                    ">=" => ComparisonOp::GtEq,
                    "AND" | "And" => {
                        return Ok(WhereClause::And(
                            Box::new(Self::convert_expr_to_where(left)?),
                            Box::new(Self::convert_expr_to_where(right)?),
                        ));
                    }
                    "OR" | "Or" => {
                        return Ok(WhereClause::Or(
                            Box::new(Self::convert_expr_to_where(left)?),
                            Box::new(Self::convert_expr_to_where(right)?),
                        ));
                    }
                    other => {
                        return Err(ParseError::Syntax(format!("不支持的运算符: {}", other))
                            .into());
                    }
                };

                let column = match left.as_ref() {
                    Expr::Identifier(id) => id.to_string(),
                    _ => {
                        return Err(ParseError::Syntax(
                            "WHERE 条件左侧必须是列名".to_string(),
                        )
                        .into())
                    }
                };

                let value = Self::expr_to_value(right.as_ref())?;

                Ok(WhereClause::Simple {
                    column,
                    operator,
                    value,
                })
            }
            _ => Err(ParseError::Syntax(format!("不支持的 WHERE 表达式: {:?}", expr)).into()),
        }
    }

    fn object_name_to_string(name: &sqlparser::ast::ObjectName) -> String {
        name.0
            .iter()
            .map(|id| id.to_string())
            .collect::<Vec<_>>()
            .join(".")
    }

    fn table_factor_to_string(tf: &sqlparser::ast::TableFactor) -> String {
        match tf {
            sqlparser::ast::TableFactor::Table { name, .. } => Self::object_name_to_string(name),
            _ => "unknown".to_string(),
        }
    }

    fn table_object_to_string(to: &sqlparser::ast::TableObject) -> String {
        match to {
            sqlparser::ast::TableObject::TableName(name) => Self::object_name_to_string(name),
            _ => to.to_string(),
        }
    }

    /// 将 FromTable 转换为表名字符串
    fn from_table_to_string(ft: &sqlparser::ast::FromTable) -> String {
        let tables = match ft {
            sqlparser::ast::FromTable::WithFromKeyword(tables) => tables,
            sqlparser::ast::FromTable::WithoutKeyword(tables) => tables,
        };
        if let Some(twj) = tables.first() {
            Self::table_factor_to_string(&twj.relation)
        } else {
            "unknown".to_string()
        }
    }

    #[allow(dead_code)]
    fn ident_to_string(id: &Ident) -> String {
        id.to_string()
    }
}

/// 对两个值的排序比较（用于 ORDER BY）
pub fn compare_values(a: &Value, b: &Value) -> std::cmp::Ordering {
    match (a, b) {
        (Value::Integer(ai), Value::Integer(bi)) => ai.cmp(bi),
        (Value::Integer(ai), Value::Float(bf)) => (*ai as f64).total_cmp(bf),
        (Value::Float(af), Value::Integer(bi)) => af.total_cmp(&(*bi as f64)),
        (Value::Float(af), Value::Float(bf)) => af.total_cmp(bf),
        (Value::Text(at), Value::Text(bt)) => at.cmp(bt),
        (Value::Timestamp(at), Value::Timestamp(bt)) => at.cmp(bt),
        (Value::Boolean(at), Value::Boolean(bt)) => at.cmp(bt),
        _ => std::cmp::Ordering::Equal,
    }
}

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

    #[test]
    fn test_parse_create_table() {
        let sql = "CREATE TABLE users (id INT PRIMARY KEY, name TEXT, age INT)";
        let stmt = SqlParser::parse(sql).unwrap();
        match stmt {
            SqlStatement::CreateTable { name, columns, .. } => {
                assert_eq!(name, "users");
                assert_eq!(columns.len(), 3);
                assert!(columns[0].is_primary_key);
                assert_eq!(columns[0].col_type, ColumnType::Integer);
                assert_eq!(columns[1].col_type, ColumnType::Text);
            }
            _ => panic!("期望 CREATE TABLE"),
        }
    }

    #[test]
    fn test_parse_select() {
        let sql = "SELECT name, age FROM users WHERE age > 18 ORDER BY age DESC LIMIT 10";
        let stmt = SqlParser::parse(sql).unwrap();
        match stmt {
            SqlStatement::Select {
                table,
                columns,
                where_clause,
                order_by,
                limit,
                ..
            } => {
                assert_eq!(table, "users");
                assert_eq!(columns, vec!["name", "age"]);
                assert!(where_clause.is_some());
                assert!(order_by.is_some());
                assert_eq!(limit, Some(10));
            }
            _ => panic!("期望 SELECT"),
        }
    }

    #[test]
    fn test_parse_insert() {
        let sql = "INSERT INTO users VALUES (1, 'Alice', 30)";
        let stmt = SqlParser::parse(sql).unwrap();
        match stmt {
            SqlStatement::Insert {
                table,
                columns,
                values,
            } => {
                assert_eq!(table, "users");
                assert!(columns.is_empty());
                assert_eq!(values.len(), 1);
                assert_eq!(values[0][0], Value::Integer(1));
            }
            _ => panic!("期望 INSERT"),
        }
    }

    #[test]
    fn test_parse_syntax_error() {
        let sql = "SLECT * FROME users";
        let result = SqlParser::parse(sql);
        assert!(result.is_err());
    }

    #[test]
    fn test_parse_update() {
        let sql = "UPDATE users SET name = 'Bob' WHERE id = 1";
        let stmt = SqlParser::parse(sql).unwrap();
        match stmt {
            SqlStatement::Update {
                table,
                assignments,
                where_clause,
            } => {
                assert_eq!(table, "users");
                assert_eq!(assignments.len(), 1);
                assert_eq!(assignments[0].0, "name");
                assert!(where_clause.is_some());
            }
            _ => panic!("期望 UPDATE"),
        }
    }

    #[test]
    fn test_parse_delete() {
        let sql = "DELETE FROM users WHERE id = 1";
        let stmt = SqlParser::parse(sql).unwrap();
        match stmt {
            SqlStatement::Delete {
                table,
                where_clause,
            } => {
                assert_eq!(table, "users");
                assert!(where_clause.is_some());
            }
            _ => panic!("期望 DELETE"),
        }
    }

    #[test]
    fn test_parse_drop_table() {
        let sql = "DROP TABLE users";
        let stmt = SqlParser::parse(sql).unwrap();
        match stmt {
            SqlStatement::DropTable { name } => {
                assert_eq!(name, "users");
            }
            _ => panic!("期望 DROP TABLE"),
        }
    }
}