scythe_codegen/backends/
csharp_npgsql.rs

1use std::fmt::Write;
2use std::path::Path;
3
4use scythe_backend::manifest::{BackendManifest, load_manifest};
5use scythe_backend::naming::{
6    enum_type_name, enum_variant_name, fn_name, row_struct_name, to_pascal_case,
7};
8use scythe_backend::types::resolve_type;
9
10use scythe_core::analyzer::{AnalyzedQuery, CompositeInfo, EnumInfo};
11use scythe_core::errors::{ErrorCode, ScytheError};
12use scythe_core::parser::QueryCommand;
13
14use crate::backend_trait::{CodegenBackend, ResolvedColumn, ResolvedParam};
15
16const DEFAULT_MANIFEST_TOML: &str = include_str!("../../manifests/csharp-npgsql.toml");
17
18pub struct CsharpNpgsqlBackend {
19    manifest: BackendManifest,
20}
21
22impl CsharpNpgsqlBackend {
23    pub fn new(engine: &str) -> Result<Self, ScytheError> {
24        match engine {
25            "postgresql" | "postgres" | "pg" => {}
26            _ => {
27                return Err(ScytheError::new(
28                    ErrorCode::InternalError,
29                    format!(
30                        "csharp-npgsql only supports PostgreSQL, got engine '{}'",
31                        engine
32                    ),
33                ));
34            }
35        }
36        let manifest_path = Path::new("backends/csharp-npgsql/manifest.toml");
37        let manifest = if manifest_path.exists() {
38            load_manifest(manifest_path)
39                .map_err(|e| ScytheError::new(ErrorCode::InternalError, format!("manifest: {e}")))?
40        } else {
41            toml::from_str(DEFAULT_MANIFEST_TOML)
42                .map_err(|e| ScytheError::new(ErrorCode::InternalError, format!("manifest: {e}")))?
43        };
44        Ok(Self { manifest })
45    }
46}
47
48/// Map a neutral type to an Npgsql reader method.
49fn reader_method(neutral_type: &str) -> &'static str {
50    match neutral_type {
51        "bool" => "GetBoolean",
52        "int16" => "GetInt16",
53        "int32" => "GetInt32",
54        "int64" => "GetInt64",
55        "float32" => "GetFloat",
56        "float64" => "GetDouble",
57        "string" | "json" | "inet" | "interval" => "GetString",
58        "uuid" => "GetGuid",
59        "decimal" => "GetDecimal",
60        "date" => "GetFieldValue<DateOnly>",
61        "time" | "time_tz" => "GetFieldValue<TimeOnly>",
62        "datetime" => "GetDateTime",
63        "datetime_tz" => "GetFieldValue<DateTimeOffset>",
64        _ => "GetValue",
65    }
66}
67
68/// Rewrite $1, $2, ... to @p1, @p2, ...
69fn rewrite_params(sql: &str) -> String {
70    let mut result = sql.to_string();
71    // Replace from highest number down to avoid $1 matching inside $10
72    for i in (1..=99).rev() {
73        let from = format!("${}", i);
74        let to = format!("@p{}", i);
75        result = result.replace(&from, &to);
76    }
77    result
78}
79
80/// Build the expression to read a column from NpgsqlDataReader.
81fn column_read_expr(col: &ResolvedColumn, ordinal: usize) -> String {
82    if col.neutral_type.starts_with("enum::") {
83        format!(
84            "(Enum.TryParse<{typ}>(reader.GetString({ord}), true, out var enumVal{ord}) ? enumVal{ord} : throw new InvalidOperationException($\"Invalid enum value '{{reader.GetString({ord})}}' for {typ}\"))",
85            typ = col.lang_type,
86            ord = ordinal
87        )
88    } else {
89        let method = reader_method(&col.neutral_type);
90        format!("reader.{}({})", method, ordinal)
91    }
92}
93
94impl CodegenBackend for CsharpNpgsqlBackend {
95    fn name(&self) -> &str {
96        "csharp-npgsql"
97    }
98
99    fn manifest(&self) -> &scythe_backend::manifest::BackendManifest {
100        &self.manifest
101    }
102
103    fn file_header(&self) -> String {
104        "// Auto-generated by scythe. Do not edit.\nusing Npgsql;\n\npublic static class Queries {"
105            .to_string()
106    }
107
108    fn file_footer(&self) -> String {
109        "}".to_string()
110    }
111
112    fn generate_row_struct(
113        &self,
114        query_name: &str,
115        columns: &[ResolvedColumn],
116    ) -> Result<String, ScytheError> {
117        let struct_name = row_struct_name(query_name, &self.manifest.naming);
118        let mut out = String::new();
119        let _ = writeln!(out, "public record {}(", struct_name);
120        for (i, c) in columns.iter().enumerate() {
121            let field = to_pascal_case(&c.field_name);
122            let sep = if i + 1 < columns.len() { "," } else { "" };
123            let _ = writeln!(out, "    {} {}{}", c.full_type, field, sep);
124        }
125        let _ = write!(out, ");");
126        Ok(out)
127    }
128
129    fn generate_model_struct(
130        &self,
131        table_name: &str,
132        columns: &[ResolvedColumn],
133    ) -> Result<String, ScytheError> {
134        let name = to_pascal_case(table_name);
135        self.generate_row_struct(&name, columns)
136    }
137
138    fn generate_query_fn(
139        &self,
140        analyzed: &AnalyzedQuery,
141        struct_name: &str,
142        columns: &[ResolvedColumn],
143        params: &[ResolvedParam],
144    ) -> Result<String, ScytheError> {
145        let func_name = fn_name(&analyzed.name, &self.manifest.naming);
146        let mut sql = rewrite_params(&super::clean_sql_oneline(&analyzed.sql));
147        // Cast enum parameters to their PG type so Npgsql sends them correctly
148        for (i, p) in params.iter().enumerate() {
149            if let Some(enum_name) = p.neutral_type.strip_prefix("enum::") {
150                let placeholder = format!("@p{}", i + 1);
151                let casted = format!("@p{}::{}", i + 1, enum_name);
152                sql = sql.replace(&placeholder, &casted);
153            }
154        }
155        let mut out = String::new();
156
157        // Build C# parameter list
158        let param_list = params
159            .iter()
160            .map(|p| format!("{} {}", p.full_type, p.field_name))
161            .collect::<Vec<_>>()
162            .join(", ");
163        let sep = if param_list.is_empty() { "" } else { ", " };
164
165        // Return type depends on command
166        let return_type = match &analyzed.command {
167            QueryCommand::One => format!("{}?", struct_name),
168            QueryCommand::Many | QueryCommand::Batch => {
169                format!("List<{}>", struct_name)
170            }
171            QueryCommand::Exec => "void".to_string(),
172            QueryCommand::ExecResult | QueryCommand::ExecRows => "int".to_string(),
173        };
174
175        let is_async_void = return_type == "void";
176        let task_type = if is_async_void {
177            "Task".to_string()
178        } else {
179            format!("Task<{}>", return_type)
180        };
181
182        let _ = writeln!(
183            out,
184            "public static async {} {}(NpgsqlConnection conn{}{}) {{",
185            task_type, func_name, sep, param_list
186        );
187
188        // Command setup
189        let _ = writeln!(
190            out,
191            "    await using var cmd = new NpgsqlCommand(\"{}\", conn);",
192            sql
193        );
194        for (i, p) in params.iter().enumerate() {
195            let value_expr = if p.neutral_type.starts_with("enum::") {
196                format!("{}.ToString().ToLower()", p.field_name)
197            } else {
198                p.field_name.clone()
199            };
200            let _ = writeln!(
201                out,
202                "    cmd.Parameters.AddWithValue(\"p{}\", {});",
203                i + 1,
204                value_expr
205            );
206        }
207
208        match &analyzed.command {
209            QueryCommand::One => {
210                let _ = writeln!(
211                    out,
212                    "    await using var reader = await cmd.ExecuteReaderAsync();"
213                );
214                let _ = writeln!(out, "    if (!await reader.ReadAsync()) return null;");
215                let _ = writeln!(out, "    return new {}(", struct_name);
216                for (i, col) in columns.iter().enumerate() {
217                    let expr = column_read_expr(col, i);
218                    let sep = if i + 1 < columns.len() { "," } else { "" };
219                    if col.nullable {
220                        let _ = writeln!(out, "        reader.IsDBNull({i}) ? null : {expr}{sep}");
221                    } else {
222                        let _ = writeln!(out, "        {expr}{sep}");
223                    }
224                }
225                let _ = writeln!(out, "    );");
226            }
227            QueryCommand::Many | QueryCommand::Batch => {
228                let _ = writeln!(
229                    out,
230                    "    await using var reader = await cmd.ExecuteReaderAsync();"
231                );
232                let _ = writeln!(out, "    var results = new List<{}>();", struct_name);
233                let _ = writeln!(out, "    while (await reader.ReadAsync()) {{");
234                let _ = writeln!(out, "        results.Add(new {}(", struct_name);
235                for (i, col) in columns.iter().enumerate() {
236                    let expr = column_read_expr(col, i);
237                    let sep = if i + 1 < columns.len() { "," } else { "" };
238                    if col.nullable {
239                        let _ =
240                            writeln!(out, "            reader.IsDBNull({i}) ? null : {expr}{sep}");
241                    } else {
242                        let _ = writeln!(out, "            {expr}{sep}");
243                    }
244                }
245                let _ = writeln!(out, "        ));");
246                let _ = writeln!(out, "    }}");
247                let _ = writeln!(out, "    return results;");
248            }
249            QueryCommand::Exec => {
250                let _ = writeln!(out, "    await cmd.ExecuteNonQueryAsync();");
251            }
252            QueryCommand::ExecResult | QueryCommand::ExecRows => {
253                let _ = writeln!(out, "    return await cmd.ExecuteNonQueryAsync();");
254            }
255        }
256
257        let _ = write!(out, "}}");
258        Ok(out)
259    }
260
261    fn generate_enum_def(&self, enum_info: &EnumInfo) -> Result<String, ScytheError> {
262        let type_name = enum_type_name(&enum_info.sql_name, &self.manifest.naming);
263        let mut out = String::new();
264        let _ = writeln!(out, "public enum {} {{", type_name);
265        for value in &enum_info.values {
266            let variant = enum_variant_name(value, &self.manifest.naming);
267            let _ = writeln!(out, "    {},", variant);
268        }
269        let _ = write!(out, "}}");
270        Ok(out)
271    }
272
273    fn generate_composite_def(&self, composite: &CompositeInfo) -> Result<String, ScytheError> {
274        let name = to_pascal_case(&composite.sql_name);
275        let mut out = String::new();
276        if composite.fields.is_empty() {
277            let _ = writeln!(out, "public record {}();", name);
278        } else {
279            let _ = writeln!(out, "public record {}(", name);
280            for (i, field) in composite.fields.iter().enumerate() {
281                let cs_type = resolve_type(&field.neutral_type, &self.manifest, false)
282                    .map(|t| t.into_owned())
283                    .unwrap_or_else(|_| "object".to_string());
284                let field_name = to_pascal_case(&field.name);
285                let sep = if i + 1 < composite.fields.len() {
286                    ","
287                } else {
288                    ""
289                };
290                let _ = writeln!(out, "    {} {}{}", cs_type, field_name, sep);
291            }
292            let _ = write!(out, ");");
293        }
294        Ok(out)
295    }
296}
scythe_codegen/backends/csharp_npgsql.rs

scythe_codegen/backends/
csharp_npgsql.rs
