// c_backend.bux — C transpiler backend (ported from c_backend.nim)
// Generates C code from the HIR.
module CBackend {

// ---------------------------------------------------------------------------
// Type → C type name
// ---------------------------------------------------------------------------

func CBackend_TypeToC(kind: int) -> String {
    if kind == tyVoid { return "void"; }
    if kind == tyBool { return "bool"; }
    if kind == tyBool8 { return "bool"; }
    if kind == tyBool16 { return "bool"; }
    if kind == tyBool32 { return "bool"; }
    if kind == tyChar8 { return "char"; }
    if kind == tyChar16 { return "uint16_t"; }
    if kind == tyChar32 { return "uint32_t"; }
    if kind == tyStr { return "const char*"; }
    if kind == tyInt8 { return "int8_t"; }
    if kind == tyInt16 { return "int16_t"; }
    if kind == tyInt32 { return "int32_t"; }
    if kind == tyInt64 { return "int64_t"; }
    if kind == tyInt{ return "int"; }
    if kind == tyUInt8 { return "uint8_t"; }
    if kind == tyUInt16 { return "uint16_t"; }
    if kind == tyUInt32 { return "uint32_t"; }
    if kind == tyUInt64 { return "uint64_t"; }
    if kind == tyUInt { return "unsigned int"; }
    if kind == tyFloat32 { return "float"; }
    if kind == tyFloat64 { return "double"; }
    if kind == tyPointer { return "void*"; }
    if kind == tyNamed { return "void*"; }
    return "int";
}

func CBackend_OpToC(op: int) -> String {
    if op == tkPlus { return "+"; }
    if op == tkMinus { return "-"; }
    if op == tkStar { return "*"; }
    if op == tkSlash { return "/"; }
    if op == tkPercent { return "%"; }
    if op == tkEq { return "=="; }
    if op == tkNe { return "!="; }
    if op == tkLt { return "<"; }
    if op == tkLe { return "<="; }
    if op == tkGt { return ">"; }
    if op == tkGe { return ">="; }
    if op == tkAmpAmp { return "&&"; }
    if op == tkPipePipe { return "||"; }
    if op == tkBang { return "!"; }
    if op == tkAmp { return "&"; }
    if op == tkPipe { return "|"; }
    if op == tkCaret { return "^"; }
    if op == tkShl { return "<<"; }
    if op == tkShr { return ">>"; }
    if op == tkAssign { return "="; }
    return "?";
}

// ---------------------------------------------------------------------------
// StringBuilder-based C emitter
// ---------------------------------------------------------------------------

struct CEmitter {
    sb: StringBuilder,
    indent: int,
}

func CBE_Init() -> CEmitter {
    var sb: StringBuilder = StringBuilder_NewCap(4096);
    return CEmitter { sb: sb, indent: 0 };
}

func CBE_Emit(cbe: *CEmitter, text: String) {
    var i: int = 0;
    while i < cbe.indent {
        StringBuilder_Append(&cbe.sb, "    ");
        i = i + 1;
    }
    StringBuilder_Append(&cbe.sb, text);
}

func CBE_EmitLine(cbe: *CEmitter, text: String) {
    CBE_Emit(cbe, text);
    StringBuilder_Append(&cbe.sb, "\n");
}

func CBE_Build(cbe: *CEmitter) -> String {
    return StringBuilder_Build(&cbe.sb);
}

// ---------------------------------------------------------------------------
// Emit HIR node
// ---------------------------------------------------------------------------

func CBE_EmitExpr(cbe: *CEmitter, node: *HirNode) {
    if node == null as *HirNode { return; }
    let kind: int = node.kind;

    // Literal
    if kind == hLit {
        StringBuilder_Append(&cbe.sb, node.strValue);
        return;
    }

    // Variable
    if kind == hVar {
        StringBuilder_Append(&cbe.sb, node.strValue);
        return;
    }

    // Binary
    if kind == hBinary {
        CBE_EmitExpr(cbe, node.child1);
        StringBuilder_Append(&cbe.sb, " ");
        StringBuilder_Append(&cbe.sb, CBackend_OpToC(node.intValue));
        StringBuilder_Append(&cbe.sb, " ");
        CBE_EmitExpr(cbe, node.child2);
        return;
    }

    // Unary
    if kind == hUnary {
        StringBuilder_Append(&cbe.sb, CBackend_OpToC(node.intValue));
        CBE_EmitExpr(cbe, node.child1);
        return;
    }

    // Call
    if kind == hCall {
        StringBuilder_Append(&cbe.sb, node.strValue);
        StringBuilder_Append(&cbe.sb, "(");
        if node.child1 != null as *HirNode {
            CBE_EmitExpr(cbe, node.child1);
        }
        if node.child2 != null as *HirNode {
            StringBuilder_Append(&cbe.sb, ", ");
            CBE_EmitExpr(cbe, node.child2);
        }
        StringBuilder_Append(&cbe.sb, ")");
        return;
    }

    // Return
    if kind == hReturn {
        StringBuilder_Append(&cbe.sb, "return");
        if node.child1 != null as *HirNode {
            StringBuilder_Append(&cbe.sb, " ");
            CBE_EmitExpr(cbe, node.child1);
        }
        return;
    }

    // Alloca
    if kind == hAlloca {
        StringBuilder_Append(&cbe.sb, CBackend_TypeToC(tyInt)); // simplified type
        StringBuilder_Append(&cbe.sb, " ");
        StringBuilder_Append(&cbe.sb, node.strValue);
        StringBuilder_Append(&cbe.sb, ";\n");
        return;
    }

    // Store: combine alloca + value into single declaration
    if kind == hStore {
        if node.child1 != null as *HirNode && node.child1.kind == hAlloca {
            // Declaration with initializer: Type x = value;
            if !String_Eq(node.child1.typeName, "") {
                StringBuilder_Append(&cbe.sb, node.child1.typeName);
            } else {
                StringBuilder_Append(&cbe.sb, CBackend_TypeToC(node.child1.intValue));
            }
            StringBuilder_Append(&cbe.sb, " ");
            StringBuilder_Append(&cbe.sb, node.child1.strValue);
            StringBuilder_Append(&cbe.sb, " = ");
            CBE_EmitExpr(cbe, node.child2);
            return;
        }
        // Plain assignment
        CBE_EmitExpr(cbe, node.child1);
        StringBuilder_Append(&cbe.sb, " = ");
        CBE_EmitExpr(cbe, node.child2);
        return;
    }

    // If
    if kind == hIf {
        StringBuilder_Append(&cbe.sb, "if (");
        CBE_EmitExpr(cbe, node.child1);
        StringBuilder_Append(&cbe.sb, ") {\n");
        if node.child2 != null as *HirNode {
            cbe.indent = cbe.indent + 1;
            CBE_EmitExpr(cbe, node.child2);
            cbe.indent = cbe.indent - 1;
        }
        var sp: int = 0;
        while sp < cbe.indent {
            StringBuilder_Append(&cbe.sb, "    ");
            sp = sp + 1;
        }
        StringBuilder_Append(&cbe.sb, "}");
        let elseBlock: *HirNode = node.extraData as *HirNode;
        if elseBlock != null as *HirNode {
            StringBuilder_Append(&cbe.sb, " else {\n");
            cbe.indent = cbe.indent + 1;
            CBE_EmitExpr(cbe, elseBlock);
            cbe.indent = cbe.indent - 1;
            sp = 0;
            while sp < cbe.indent {
                StringBuilder_Append(&cbe.sb, "    ");
                sp = sp + 1;
            }
            StringBuilder_Append(&cbe.sb, "}\n");
        } else {
            StringBuilder_Append(&cbe.sb, "\n");
        }
        return;
    }

    // Cast
    if kind == hCast {
        StringBuilder_Append(&cbe.sb, "((");
        StringBuilder_Append(&cbe.sb, CBackend_TypeToC(tyPointer));
        StringBuilder_Append(&cbe.sb, ")");
        CBE_EmitExpr(cbe, node.child1);
        StringBuilder_Append(&cbe.sb, ")");
        return;
    }

    // Struct init: ((TypeName){.field = value, ...})
    if kind == hStructInit {
        StringBuilder_Append(&cbe.sb, "((");
        StringBuilder_Append(&cbe.sb, node.strValue);
        StringBuilder_Append(&cbe.sb, "){");
        // Emit fields (chained via child3)
        var field: *HirNode = node.child1;
        var first: bool = true;
        while field != null as *HirNode {
            if !first {
                StringBuilder_Append(&cbe.sb, ", ");
            }
            StringBuilder_Append(&cbe.sb, ".");
            StringBuilder_Append(&cbe.sb, field.strValue);
            StringBuilder_Append(&cbe.sb, " = ");
            CBE_EmitExpr(cbe, field.child1);
            first = false;
            field = field.child3;
        }
        StringBuilder_Append(&cbe.sb, "})");
        return;
    }

    // Block — emit each statement via child3 linked list
    if kind == hBlock {
        var child: *HirNode = node.child1;
        while child != null as *HirNode {
            // Indent
            var sp: int = 0;
            while sp < cbe.indent {
                StringBuilder_Append(&cbe.sb, "    ");
                sp = sp + 1;
            }
            CBE_EmitExpr(cbe, child);
            // Add semicolon for statements that need it
            if child.kind != hBlock && child.kind != hIf && child.kind != hWhile && child.kind != hLoop {
                StringBuilder_Append(&cbe.sb, ";");
            }
            StringBuilder_Append(&cbe.sb, "\n");
            child = child.child3;
        }
        return;
    }
}

// ---------------------------------------------------------------------------
// Emit function declaration
// ---------------------------------------------------------------------------

func CBE_EmitFuncDecl(cbe: *CEmitter, f: *HirFunc) {
    // Return type
    if String_Eq(f.retTypeName, "") || String_Eq(f.retTypeName, "void") {
        StringBuilder_Append(&cbe.sb, "void ");
    } else if String_Eq(f.retTypeName, "String") || String_Eq(f.retTypeName, "str") {
        StringBuilder_Append(&cbe.sb, "const char* ");
    } else if String_Eq(f.retTypeName, "bool") {
        StringBuilder_Append(&cbe.sb, "bool ");
    } else if String_Eq(f.retTypeName, "int") {
        StringBuilder_Append(&cbe.sb, "int ");
    } else if String_Eq(f.retTypeName, "int64") {
        StringBuilder_Append(&cbe.sb, "int64_t ");
    } else if String_Eq(f.retTypeName, "uint") {
        StringBuilder_Append(&cbe.sb, "unsigned int ");
    } else if String_Eq(f.retTypeName, "float64") {
        StringBuilder_Append(&cbe.sb, "double ");
    } else if f.retTypeKind == tyNamed || String_StartsWith(f.retTypeName, "struct ") {
        // Use the struct name directly (e.g., "Point", "Type")
        StringBuilder_Append(&cbe.sb, f.retTypeName);
        StringBuilder_Append(&cbe.sb, " ");
    } else {
        StringBuilder_Append(&cbe.sb, "int "); // fallback
    }

    StringBuilder_Append(&cbe.sb, f.name);
    StringBuilder_Append(&cbe.sb, "(");

    // Parameters
    var i: int = 0;
    while i < f.paramCount {
        if i > 0 {
            StringBuilder_Append(&cbe.sb, ", ");
        }
        // Use param type info
        var pname: String = "";
        var ptype: String = "";
        if i == 0 { pname = f.param0.name; ptype = f.param0.typeName; }
        if i == 1 { pname = f.param1.name; ptype = f.param1.typeName; }
        if i == 2 { pname = f.param2.name; ptype = f.param2.typeName; }
        if i == 3 { pname = f.param3.name; ptype = f.param3.typeName; }
        if i == 4 { pname = f.param4.name; ptype = f.param4.typeName; }
        if i == 5 { pname = f.param5.name; ptype = f.param5.typeName; }
        // Emit type
        if String_Eq(ptype, "String") || String_Eq(ptype, "str") {
            StringBuilder_Append(&cbe.sb, "const char* ");
        } else if String_Eq(ptype, "bool") {
            StringBuilder_Append(&cbe.sb, "bool ");
        } else if String_Eq(ptype, "int") {
            StringBuilder_Append(&cbe.sb, "int ");
        } else if String_Eq(ptype, "int64") {
            StringBuilder_Append(&cbe.sb, "int64_t ");
        } else if String_Eq(ptype, "uint") {
            StringBuilder_Append(&cbe.sb, "unsigned int ");
        } else if String_Eq(ptype, "float64") {
            StringBuilder_Append(&cbe.sb, "double ");
        } else {
            StringBuilder_Append(&cbe.sb, "int "); // fallback
        }
        StringBuilder_Append(&cbe.sb, pname);
        i = i + 1;
    }

    StringBuilder_Append(&cbe.sb, ")");
}

// ---------------------------------------------------------------------------
// Generate complete C module
// ---------------------------------------------------------------------------

func CBackend_Generate(mod: *HirModule) -> String {
    let cbe: *CEmitter = bux_alloc(sizeof(CEmitter)) as *CEmitter;
    cbe.sb = StringBuilder_NewCap(8192);
    cbe.indent = 0;

    // Header
    StringBuilder_Append(&cbe.sb, "// Generated by Bux C Backend\n");
    StringBuilder_Append(&cbe.sb, "#include <stdint.h>\n");
    StringBuilder_Append(&cbe.sb, "#include <stdbool.h>\n");
    StringBuilder_Append(&cbe.sb, "#include <string.h>\n");
    StringBuilder_Append(&cbe.sb, "#include <stdio.h>\n");
    StringBuilder_Append(&cbe.sb, "#include <stdlib.h>\n\n");

    // Extern declarations
    var i: int = 0;
    while i < mod.externCount {
        CBE_EmitFuncDecl(cbe, &mod.externFuncs[i]);
        StringBuilder_Append(&cbe.sb, ";\n");
        i = i + 1;
    }
    StringBuilder_Append(&cbe.sb, "\n");

    // Function definitions
    var hasMain: bool = false;
    i = 0;
    while i < mod.funcCount {
        if String_Eq(mod.funcs[i].name, "Main") { hasMain = true; }
        CBE_EmitFuncDecl(cbe, &mod.funcs[i]);
        StringBuilder_Append(&cbe.sb, " {\n");
        // Body
        var hasReturn: bool = false;
        let body: *HirNode = mod.funcs[i].body;
        if body != null as *HirNode {
            cbe.indent = 1;
            CBE_EmitExpr(cbe, body);
            cbe.indent = 0;
            // Check if body has a return statement
            var stmt: *HirNode = body.child1;
            while stmt != null as *HirNode {
                if stmt.kind == hReturn { hasReturn = true; }
                stmt = stmt.child3;
            }
        }
        // Add default return 0 only if function returns int and has no explicit return
        if String_Eq(mod.funcs[i].retTypeName, "int") && !hasReturn {
            StringBuilder_Append(&cbe.sb, "    return 0;\n");
        }
        StringBuilder_Append(&cbe.sb, "}\n\n");
        i = i + 1;
    }

    // Generate C main wrapper if Main function exists
    if hasMain {
        StringBuilder_Append(&cbe.sb, "extern int g_argc;\n");
        StringBuilder_Append(&cbe.sb, "extern char** g_argv;\n");
        StringBuilder_Append(&cbe.sb, "int main(int argc, char** argv) {\n");
        StringBuilder_Append(&cbe.sb, "    g_argc = argc;\n");
        StringBuilder_Append(&cbe.sb, "    g_argv = argv;\n");
        StringBuilder_Append(&cbe.sb, "    return Main();\n");
        StringBuilder_Append(&cbe.sb, "}\n");
    }

    return StringBuilder_Build(&cbe.sb);
}

func CBackend_Free(cbe: *CEmitter) {
    StringBuilder_Free(&cbe.sb);
    bux_free(cbe as *void);
}
}