From acf79a306797b1b12e95415c340792d7c88815ab Mon Sep 17 00:00:00 2001
From: Melody Horn / boringcactus <melody@boringcactus.com>
Date: Fri, 18 Jun 2021 13:42:52 -0600
Subject: lay groundwork for make-migrations

---
 src/cli/make_migrations.rs | 66 ++++++++++++++++++++++++++++++++++++++++++++++
 src/cli/mod.rs             |  3 +++
 src/db/models/meta.rs      |  3 +++
 src/db/models/mod.rs       |  1 +
 tosin-macros/src/lib.rs    |  4 ++-
 5 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 src/cli/make_migrations.rs

diff --git a/src/cli/make_migrations.rs b/src/cli/make_migrations.rs
new file mode 100644
index 0000000..767639f
--- /dev/null
+++ b/src/cli/make_migrations.rs
@@ -0,0 +1,66 @@
+use std::collections::HashMap;
+
+use structopt::StructOpt;
+
+use crate::{Settings, UrlMap, db::backend::Connectable};
+use crate::db::migration::{Migration, DatabaseChange, CreateModelOption};
+use crate::db::models::{Field, ModelMeta};
+
+#[derive(StructOpt)]
+/// Generate migrations
+pub struct MakeMigrations {
+}
+
+#[derive(Debug)]
+struct AppTablesState {
+    db: HashMap<&'static str, TableState>,
+}
+
+#[derive(Debug)]
+struct TableState {
+    fields: Vec<Field>,
+}
+
+impl From<&[ModelMeta]> for AppTablesState {
+    fn from(models: &[ModelMeta]) -> Self {
+        let mut db = HashMap::new();
+        for model in models {
+            db.insert(model.name, TableState { fields: model.fields.into() });
+        }
+        Self { db }
+    }
+}
+
+impl From<&[Migration]> for AppTablesState {
+    fn from(migrations: &[Migration]) -> Self {
+        let mut db = HashMap::new();
+        for migration in migrations {
+            for change in migration.changes {
+                match change {
+                    DatabaseChange::CreateModel { name, fields, options } => {
+                        if db.contains_key(name) {
+                            if options.contains(&CreateModelOption::IfNotExist) {
+                                continue;
+                            } else {
+                                panic!("double-created table {}", name);
+                            }
+                        }
+                        db.insert(*name, TableState { fields: (*fields).into() });
+                    }
+                }
+            }
+        }
+        Self { db }
+    }
+}
+
+impl MakeMigrations {
+    pub fn execute(self, _urls: UrlMap, settings: Settings<impl Connectable>) {
+        for app in settings.installed_apps {
+            let expected_table_state = AppTablesState::from(app.models);
+            let actual_table_state = AppTablesState::from(app.migrations);
+            dbg!(expected_table_state, actual_table_state);
+            todo!();
+        }
+    }
+}
diff --git a/src/cli/mod.rs b/src/cli/mod.rs
index a11fd48..851812f 100644
--- a/src/cli/mod.rs
+++ b/src/cli/mod.rs
@@ -2,11 +2,13 @@ use structopt::StructOpt;
 
 use crate::{Settings, UrlMap, db::backend::Connectable};
 
+mod make_migrations;
 mod migrate;
 mod run_server;
 
 #[derive(StructOpt)]
 enum Command {
+    MakeMigrations(make_migrations::MakeMigrations),
     Migrate(migrate::Migrate),
     RunServer(run_server::RunServer),
 }
@@ -14,6 +16,7 @@ enum Command {
 impl Command {
     fn execute(self, urls: UrlMap, settings: Settings<impl Connectable>) {
         match self {
+            Command::MakeMigrations(command) => command.execute(urls, settings),
             Command::Migrate(command) => command.execute(urls, settings),
             Command::RunServer(command) => command.execute(urls, settings),
         }
diff --git a/src/db/models/meta.rs b/src/db/models/meta.rs
index 50729a8..16e7290 100644
--- a/src/db/models/meta.rs
+++ b/src/db/models/meta.rs
@@ -1,3 +1,6 @@
+use super::Field;
+
 pub struct ModelMeta {
     pub name: &'static str,
+    pub fields: &'static [Field],
 }
diff --git a/src/db/models/mod.rs b/src/db/models/mod.rs
index feadb43..3f39ccd 100644
--- a/src/db/models/mod.rs
+++ b/src/db/models/mod.rs
@@ -5,6 +5,7 @@ pub use meta::*;
 
 pub type Id = usize;
 
+#[derive(Clone, Debug)]
 pub enum Field {
     CharField {
         name: &'static str,
diff --git a/tosin-macros/src/lib.rs b/tosin-macros/src/lib.rs
index 531a92b..86750e1 100644
--- a/tosin-macros/src/lib.rs
+++ b/tosin-macros/src/lib.rs
@@ -20,9 +20,11 @@ pub fn model_derive(input: TokenStream) -> TokenStream {
 fn impl_model(ast: &syn::DeriveInput) -> TokenStream {
     let name = &ast.ident;
     let gen = quote! {
+        use tosin::db::models::ModelMeta;
         impl #name {
-            pub const META: tosin::db::models::ModelMeta = tosin::db::models::ModelMeta {
+            pub const META: ModelMeta = ModelMeta {
                 name: stringify!(#name),
+                fields: &[],
             };
         }
     };
-- 
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