From 2615cdce2c8af5e0001fc1a70cb88698109b52f1 Mon Sep 17 00:00:00 2001
From: Pekka Enberg <penberg@iki.fi>
Date: Sun, 27 Aug 2023 20:40:12 +0300
Subject: [PATCH] Schema in-memory data structures

---
 core/lib.rs    |   1 +
 core/schema.rs | 114 +++++++++++++++++++++++++++++++++++++++++++++++++
 core/vdbe.rs   |   3 ++
 3 files changed, 118 insertions(+)
 create mode 100644 core/schema.rs

diff --git a/core/lib.rs b/core/lib.rs
index c07770ab2..de4ef7a3a 100644
--- a/core/lib.rs
+++ b/core/lib.rs
@@ -1,5 +1,6 @@
 mod buffer_pool;
 mod pager;
+mod schema;
 mod sqlite3_ondisk;
 mod vdbe;
 
diff --git a/core/schema.rs b/core/schema.rs
new file mode 100644
index 000000000..43618dc03
--- /dev/null
+++ b/core/schema.rs
@@ -0,0 +1,114 @@
+use core::fmt;
+use std::collections::HashMap;
+
+pub struct Schema {
+    pub tables: HashMap<String, Table>,
+}
+
+impl Schema {
+    pub fn new() -> Self {
+        let mut tables: HashMap<String, Table> = HashMap::new();
+        tables.insert("sqlite_schema".to_string(), sqlite_schema_table());
+        Self { tables }
+    }
+
+    pub fn add_table(&mut self, name: String, table: Table) {
+        self.tables.insert(name, table);
+    }
+}
+
+pub struct Table {
+    root_page: i32,
+    name: String,
+    columns: Vec<Column>,
+}
+
+impl Table {
+    pub fn to_sql(&self) -> String {
+        let mut sql = format!("CREATE TABLE {} (\n", self.name);
+        for (i, column) in self.columns.iter().enumerate() {
+            if i > 0 {
+                sql.push_str(",\n");
+            }
+            sql.push_str("  ");
+            sql.push_str(&column.name);
+            sql.push_str(" ");
+            sql.push_str(&column.ty.to_string());
+        }
+        sql.push_str(");\n");
+        sql
+    }
+}
+
+pub struct Column {
+    name: String,
+    ty: Type,
+}
+
+pub enum Type {
+    Null,
+    Integer,
+    Real,
+    Text,
+    Blob,
+}
+
+impl fmt::Display for Type {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let s = match self {
+            Type::Null => "NULL",
+            Type::Integer => "INTEGER",
+            Type::Real => "REAL",
+            Type::Text => "TEXT",
+            Type::Blob => "BLOB",
+        };
+        write!(f, "{}", s)
+    }
+}
+
+pub fn sqlite_schema_table() -> Table {
+    Table {
+        root_page: 1,
+        name: "sqlite_schema".to_string(),
+        columns: vec![
+            Column {
+                name: "type".to_string(),
+                ty: Type::Text,
+            },
+            Column {
+                name: "name".to_string(),
+                ty: Type::Text,
+            },
+            Column {
+                name: "tbl_name".to_string(),
+                ty: Type::Text,
+            },
+            Column {
+                name: "rootpage".to_string(),
+                ty: Type::Integer,
+            },
+            Column {
+                name: "sql".to_string(),
+                ty: Type::Text,
+            },
+        ],
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    pub fn test_sqlite_schema() {
+        let expected = r#"CREATE TABLE sqlite_schema (
+  type TEXT,
+  name TEXT,
+  tbl_name TEXT,
+  rootpage INTEGER,
+  sql TEXT);
+"#;
+        let actual = sqlite_schema_table().to_sql();
+        assert_eq!(expected, actual);
+    }
+}
diff --git a/core/vdbe.rs b/core/vdbe.rs
index beb7dff48..8fb081939 100644
--- a/core/vdbe.rs
+++ b/core/vdbe.rs
@@ -1,4 +1,5 @@
 use crate::pager::Pager;
+use crate::schema::Schema;
 
 use anyhow::Result;
 use sqlite3_parser::ast::{Select, Stmt};
@@ -31,6 +32,7 @@ pub struct GotoInsn {
     pub target_pc: usize,
 }
 pub struct Program {
+    pub schema: Schema,
     pub insns: Vec<Insn>,
     pub pc: usize,
 }
@@ -64,6 +66,7 @@ impl ProgramBuilder {
 
     pub fn build(self) -> Program {
         Program {
+            schema: Schema::new(),
             insns: self.insns,
             pc: 0,
         }