package lang

import (
	"fmt"
	"strconv"
	"strings"
)

type sqlCallStep struct {
	name string
	call CallExpr
}

type sqlLowered struct {
	value     string
	result    ClassDecl
	hasResult bool
}

func splitSQLChain(expr Expr) (CallExpr, string, []sqlCallStep, bool) {
	var reversed []sqlCallStep
	current := expr
	for {
		call, ok := current.(CallExpr)
		if !ok {
			return CallExpr{}, "", nil, false
		}
		selector, ok := call.Callee.(SelectorExpr)
		if !ok {
			return CallExpr{}, "", nil, false
		}
		if receiver, ok := selector.Receiver.(IdentExpr); ok && receiver.Name == "sql" {
			switch selector.Name {
			case "from", "insert", "update", "delete":
			default:
				return CallExpr{}, "", nil, false
			}
			steps := make([]sqlCallStep, len(reversed))
			for i := range reversed {
				steps[len(reversed)-1-i] = reversed[i]
			}
			return call, selector.Name, steps, true
		}
		reversed = append(reversed, sqlCallStep{name: selector.Name, call: call})
		current = selector.Receiver
	}
}

func (g *goGenerator) lowerSQLQuery(expr Expr) (string, bool, error) {
	root, operation, steps, ok := splitSQLChain(expr)
	if !ok {
		return "", false, nil
	}
	if len(steps) == 0 {
		return "", true, sqlTerminalError(operation)
	}
	terminal := steps[len(steps)-1]
	switch terminal.name {
	case "build":
		if len(terminal.call.Args) != 0 || len(terminal.call.NamedArgs) != 0 || len(terminal.call.TypeArgs) != 0 {
			return "", true, fmt.Errorf("SQL build() does not accept arguments")
		}
	case "fetch", "single", "iterator":
		if err := g.validateSQLExecutionTerminal(terminal); err != nil {
			return "", true, err
		}
	default:
		return "", true, sqlTerminalError(operation)
	}
	steps = steps[:len(steps)-1]

	var lowered sqlLowered
	var err error
	switch operation {
	case "from":
		lowered, err = g.lowerSQLSelect(root, steps)
	case "insert":
		lowered, err = g.lowerSQLInsert(root, steps)
	case "update":
		lowered, err = g.lowerSQLUpdate(root, steps)
	case "delete":
		lowered, err = g.lowerSQLDelete(root, steps)
	default:
		err = fmt.Errorf("unsupported sql operation %q", operation)
	}
	if err != nil || terminal.name == "build" {
		return lowered.value, true, err
	}
	if !lowered.hasResult {
		return "", true, fmt.Errorf("SQL %s() is only supported for sql.from or writes with returning(); sql.%s requires returning()", terminal.name, operation)
	}
	pool, err := g.expr(terminal.call.Args[0], "")
	if err != nil {
		return "", true, err
	}
	ctx, err := g.expr(terminal.call.Args[1], "")
	if err != nil {
		return "", true, err
	}
	helper := map[string]string{
		"fetch":    "gotlinSQLFetch",
		"single":   "gotlinSQLSingle",
		"iterator": "gotlinSQLIterate",
	}[terminal.name]
	return fmt.Sprintf("%s[%s](%s, %s, %s, gotlinSQLScan%s)", helper, lowered.result.Name, pool, ctx, lowered.value, lowered.result.Name), true, nil
}

func sqlTerminalError(operation string) error {
	return fmt.Errorf("sql.%s query must end with build(), fetch(pool, ctx), single(pool, ctx), or iterator(pool, ctx)", operation)
}

func (g *goGenerator) validateSQLExecutionTerminal(terminal sqlCallStep) error {
	call := terminal.call
	if len(call.TypeArgs) != 0 || len(call.NamedArgs) != 0 || len(call.Args) != 2 {
		return fmt.Errorf("SQL %s() expects exactly pool and ctx positional arguments", terminal.name)
	}
	if typ := g.exprType(call.Args[0]); sqlInvalidExecutionArgType(typ) {
		return fmt.Errorf("SQL %s() pool argument has non-query type %s", terminal.name, typ)
	}
	if typ := g.exprType(call.Args[1]); sqlInvalidExecutionArgType(typ) {
		return fmt.Errorf("SQL %s() ctx argument has non-context type %s", terminal.name, typ)
	}
	return nil
}

func sqlInvalidExecutionArgType(typ string) bool {
	switch sqlBaseType(typ) {
	case "Int", "Float", "Double", "String", "Boolean", "Unit", "ByteSlice":
		return true
	default:
		return false
	}
}

func sqlChainResultType(expr Expr) (string, bool) {
	root, operation, steps, ok := splitSQLChain(expr)
	if !ok || len(root.TypeArgs) != 1 || len(steps) == 0 {
		return "", false
	}
	terminal := steps[len(steps)-1].name
	if terminal == "build" {
		return "GotlinSQLQuery", true
	}
	if terminal != "fetch" && terminal != "single" && terminal != "iterator" {
		return "", false
	}
	resultType := root.TypeArgs[0]
	if operation == "from" {
		for _, step := range steps[:len(steps)-1] {
			if step.name == "select" {
				if typ, ok := sqlProjectionType(step.call, resultType); ok {
					resultType = typ
				}
			}
		}
	} else {
		found := false
		for _, step := range steps[:len(steps)-1] {
			if step.name == "returning" {
				resultType, found = sqlProjectionType(step.call, resultType)
			}
		}
		if !found {
			return "", false
		}
	}
	switch terminal {
	case "fetch":
		return "List<*" + resultType + ">", true
	case "single":
		return "*" + resultType, true
	case "iterator":
		return "GotlinSQLIterator<" + resultType + ">", true
	default:
		return "", false
	}
}

func sqlProjectionType(call CallExpr, rowType string) (string, bool) {
	lambda, err := sqlLambdaArg(call, "projection")
	if err != nil {
		return "", false
	}
	rowName := "it"
	if !lambda.ImplicitIt {
		if len(lambda.Params) != 1 {
			return "", false
		}
		rowName = lambda.Params[0].Name
	}
	if len(lambda.Body) != 1 {
		return "", false
	}
	stmt, ok := lambda.Body[0].(ExprStmt)
	if !ok {
		return "", false
	}
	if ident, ok := stmt.Value.(IdentExpr); ok && ident.Name == rowName {
		return rowType, true
	}
	constructor, ok := stmt.Value.(CallExpr)
	if !ok || len(constructor.NamedArgs) != 0 || len(constructor.TypeArgs) != 0 {
		return "", false
	}
	ident, ok := constructor.Callee.(IdentExpr)
	return ident.Name, ok
}

func (g *goGenerator) sqlClass(root CallExpr, operation string) (ClassDecl, error) {
	if len(root.TypeArgs) != 1 {
		return ClassDecl{}, fmt.Errorf("sql.%s expects exactly one row type", operation)
	}
	class, ok := g.classes[root.TypeArgs[0]]
	if !ok {
		return ClassDecl{}, fmt.Errorf("SQL row class %q does not exist", root.TypeArgs[0])
	}
	if !class.Data {
		return ClassDecl{}, fmt.Errorf("SQL row class %s must be a data class", class.Name)
	}
	if class.Table == "" {
		return ClassDecl{}, fmt.Errorf("SQL row class %s requires @table", class.Name)
	}
	columns := map[string]string{}
	for _, field := range class.Fields {
		column := sqlColumn(field)
		if previous, exists := columns[column]; exists {
			return ClassDecl{}, fmt.Errorf("SQL fields %s and %s map to duplicate column %q", previous, field.Name, column)
		}
		columns[column] = field.Name
	}
	return class, nil
}

func (g *goGenerator) lowerSQLSelect(root CallExpr, steps []sqlCallStep) (sqlLowered, error) {
	if len(root.Args) != 0 || len(root.NamedArgs) != 0 {
		return sqlLowered{}, fmt.Errorf("sql.from does not accept value arguments")
	}
	class, err := g.sqlClass(root, "from")
	if err != nil {
		return sqlLowered{}, err
	}
	columns := sqlAllColumns(class)
	result := class
	var where, order, limit string
	var args []string
	stage := 0
	seenSelect := false
	seenWhere := false
	seenOrder := false
	seenLimit := false
	seenForUpdate := false
	seenSkipLocked := false
	for _, step := range steps {
		switch step.name {
		case "select":
			if seenSelect || stage != 0 {
				return sqlLowered{}, fmt.Errorf("select() may appear once and must be the first sql.from method")
			}
			result, columns, err = g.sqlProjection(step.call, class, "select")
			if err != nil {
				return sqlLowered{}, err
			}
			seenSelect = true
			stage = 1
		case "where":
			if seenWhere || stage > 1 {
				return sqlLowered{}, fmt.Errorf("where() may appear once after select() and before ordering")
			}
			where, args, err = g.sqlWhere(step.call, class, len(args)+1)
			if err != nil {
				return sqlLowered{}, err
			}
			seenWhere = true
			stage = 2
		case "orderBy", "orderByDescending":
			if seenOrder || stage > 2 {
				return sqlLowered{}, fmt.Errorf("orderBy()/orderByDescending() may appear once before limit()")
			}
			order, err = sqlOrder(step, class)
			if err != nil {
				return sqlLowered{}, err
			}
			seenOrder = true
			stage = 3
		case "limit":
			if seenLimit || stage > 3 {
				return sqlLowered{}, fmt.Errorf("limit() may appear once after ordering and before forUpdate()")
			}
			var limitArgs []string
			limit, limitArgs, err = g.sqlLimit(step.call)
			if err != nil {
				return sqlLowered{}, err
			}
			if limit == "?" {
				limit = "$" + strconv.Itoa(len(args)+1)
			}
			args = append(args, limitArgs...)
			seenLimit = true
			stage = 4
		case "forUpdate":
			if seenForUpdate || stage > 4 || !sqlNoArgs(step.call) {
				return sqlLowered{}, fmt.Errorf("forUpdate() accepts no arguments and must appear once after limit()")
			}
			seenForUpdate = true
			stage = 5
		case "skipLocked":
			if seenSkipLocked || !seenForUpdate || stage != 5 || !sqlNoArgs(step.call) {
				return sqlLowered{}, fmt.Errorf("skipLocked() accepts no arguments and requires a preceding forUpdate()")
			}
			seenSkipLocked = true
			stage = 6
		default:
			return sqlLowered{}, fmt.Errorf("unsupported sql.from method %q", step.name)
		}
	}
	query := "SELECT " + strings.Join(columns, ", ") + " FROM " + class.Table
	if where != "" {
		query += " WHERE " + where
	}
	if order != "" {
		query += " ORDER BY " + order
	}
	if limit != "" {
		query += " LIMIT " + limit
	}
	if seenForUpdate {
		query += " FOR UPDATE"
	}
	if seenSkipLocked {
		query += " SKIP LOCKED"
	}
	return sqlLowered{value: sqlQueryValue(query, args), result: result, hasResult: true}, nil
}

func (g *goGenerator) lowerSQLInsert(root CallExpr, steps []sqlCallStep) (sqlLowered, error) {
	if len(root.Args) != 1 || len(root.NamedArgs) != 0 {
		return sqlLowered{}, fmt.Errorf("sql.insert expects exactly one row argument")
	}
	class, err := g.sqlClass(root, "insert")
	if err != nil {
		return sqlLowered{}, err
	}
	if typ := strings.TrimPrefix(g.exprType(root.Args[0]), "*"); typ == "" {
		return sqlLowered{}, fmt.Errorf("sql.insert row argument requires a known type")
	} else if typ != class.Name {
		return sqlLowered{}, fmt.Errorf("sql.insert<%s> cannot insert value of type %s", class.Name, typ)
	}
	row, err := g.expr(root.Args[0], class.Name)
	if err != nil {
		return sqlLowered{}, err
	}
	var columns, placeholders, args []string
	for _, field := range class.Fields {
		if field.Generated {
			continue
		}
		columns = append(columns, sqlColumn(field))
		placeholders = append(placeholders, "$"+strconv.Itoa(len(args)+1))
		args = append(args, sqlGoField(row, root.Args[0], class, field))
	}
	query := "INSERT INTO " + class.Table
	if len(columns) == 0 {
		query += " DEFAULT VALUES"
	} else {
		query += " (" + strings.Join(columns, ", ") + ") VALUES (" + strings.Join(placeholders, ", ") + ")"
	}

	index := 0
	if index < len(steps) && steps[index].name == "onConflict" {
		conflictLambda, err := sqlLambdaArg(steps[index].call, "onConflict")
		if err != nil {
			return sqlLowered{}, err
		}
		rowName, body, err := sqlLambdaExpr(conflictLambda, class, "onConflict")
		if err != nil {
			return sqlLowered{}, err
		}
		conflictFields, err := sqlConflictFields(body, class, rowName)
		if err != nil {
			return sqlLowered{}, err
		}
		var conflictColumns []string
		for _, field := range conflictFields {
			if !field.ID {
				return sqlLowered{}, fmt.Errorf("onConflict field %s must be annotated @id", field.Name)
			}
			conflictColumns = append(conflictColumns, sqlColumn(field))
		}
		query += " ON CONFLICT (" + strings.Join(conflictColumns, ", ") + ")"
		index++
		if index >= len(steps) {
			return sqlLowered{}, fmt.Errorf("onConflict() requires doNothing() or doUpdate()")
		}
		action := steps[index]
		switch action.name {
		case "doNothing":
			if !sqlNoArgs(action.call) {
				return sqlLowered{}, fmt.Errorf("doNothing() does not accept arguments")
			}
			query += " DO NOTHING"
		case "doUpdate":
			lambda, err := sqlLambdaArg(action.call, "doUpdate")
			if err != nil {
				return sqlLowered{}, err
			}
			assignments, err := sqlConflictUpdateAssignments(lambda, class)
			if err != nil {
				return sqlLowered{}, err
			}
			query += " DO UPDATE SET " + strings.Join(assignments, ", ")
		default:
			return sqlLowered{}, fmt.Errorf("onConflict() requires doNothing() or doUpdate(), found %s()", action.name)
		}
		index++
	}

	lowered := sqlLowered{}
	if index < len(steps) && steps[index].name == "returning" {
		result, returning, err := g.sqlProjection(steps[index].call, class, "returning")
		if err != nil {
			return sqlLowered{}, err
		}
		query += " RETURNING " + strings.Join(returning, ", ")
		lowered.result = result
		lowered.hasResult = true
		index++
	}
	if index != len(steps) {
		return sqlLowered{}, fmt.Errorf("unsupported sql.insert method %q or invalid method order", steps[index].name)
	}
	lowered.value = sqlQueryValue(query, args)
	return lowered, nil
}

func (g *goGenerator) lowerSQLUpdate(root CallExpr, steps []sqlCallStep) (sqlLowered, error) {
	if len(root.Args) != 0 || len(root.NamedArgs) != 0 {
		return sqlLowered{}, fmt.Errorf("sql.update does not accept value arguments")
	}
	class, err := g.sqlClass(root, "update")
	if err != nil {
		return sqlLowered{}, err
	}
	if len(steps) == 0 || steps[0].name != "set" {
		return sqlLowered{}, fmt.Errorf("sql.update requires set() as its first method")
	}
	assignments, args, err := g.sqlTypedUpdateAssignments(steps[0].call, class)
	if err != nil {
		return sqlLowered{}, err
	}
	query := "UPDATE " + class.Table + " SET " + postgresPlaceholders(strings.Join(assignments, ", "), 1)
	index := 1
	if index < len(steps) && steps[index].name == "where" {
		where, whereArgs, err := g.sqlWhere(steps[index].call, class, len(args)+1)
		if err != nil {
			return sqlLowered{}, err
		}
		query += " WHERE " + where
		args = append(args, whereArgs...)
		index++
	}
	lowered := sqlLowered{}
	if index < len(steps) && steps[index].name == "returning" {
		result, returning, err := g.sqlProjection(steps[index].call, class, "returning")
		if err != nil {
			return sqlLowered{}, err
		}
		query += " RETURNING " + strings.Join(returning, ", ")
		lowered.result = result
		lowered.hasResult = true
		index++
	}
	if index != len(steps) {
		return sqlLowered{}, fmt.Errorf("unsupported sql.update method %q or invalid method order", steps[index].name)
	}
	lowered.value = sqlQueryValue(query, args)
	return lowered, nil
}

func (g *goGenerator) lowerSQLDelete(root CallExpr, steps []sqlCallStep) (sqlLowered, error) {
	if len(root.Args) != 0 || len(root.NamedArgs) != 0 {
		return sqlLowered{}, fmt.Errorf("sql.delete does not accept value arguments")
	}
	class, err := g.sqlClass(root, "delete")
	if err != nil {
		return sqlLowered{}, err
	}
	query := "DELETE FROM " + class.Table
	var args []string
	index := 0
	if index < len(steps) && steps[index].name == "where" {
		where, whereArgs, err := g.sqlWhere(steps[index].call, class, 1)
		if err != nil {
			return sqlLowered{}, err
		}
		query += " WHERE " + where
		args = whereArgs
		index++
	}
	lowered := sqlLowered{}
	if index < len(steps) && steps[index].name == "returning" {
		result, returning, err := g.sqlProjection(steps[index].call, class, "returning")
		if err != nil {
			return sqlLowered{}, err
		}
		query += " RETURNING " + strings.Join(returning, ", ")
		lowered.result = result
		lowered.hasResult = true
		index++
	}
	if index != len(steps) {
		return sqlLowered{}, fmt.Errorf("unsupported sql.delete method %q or invalid method order", steps[index].name)
	}
	lowered.value = sqlQueryValue(query, args)
	return lowered, nil
}

func sqlGoField(row string, source Expr, class ClassDecl, field FieldDecl) string {
	fieldName := field.Name
	if class.Data && !field.Private {
		fieldName = exportedGoName(fieldName)
	}
	receiver := row
	switch source.(type) {
	case IdentExpr, SelectorExpr, IndexExpr:
	default:
		receiver = "(" + receiver + ")"
	}
	return receiver + "." + fieldName
}

func sqlAllColumns(class ClassDecl) []string {
	columns := make([]string, 0, len(class.Fields))
	for _, field := range class.Fields {
		columns = append(columns, sqlColumn(field))
	}
	return columns
}

func (g *goGenerator) sqlProjection(call CallExpr, rowClass ClassDecl, method string) (ClassDecl, []string, error) {
	lambda, err := sqlLambdaArg(call, method)
	if err != nil {
		return ClassDecl{}, nil, err
	}
	rowName, body, err := sqlLambdaExpr(lambda, rowClass, method)
	if err != nil {
		return ClassDecl{}, nil, err
	}
	if ident, ok := body.(IdentExpr); ok && ident.Name == rowName {
		return rowClass, sqlAllColumns(rowClass), nil
	}
	constructor, ok := body.(CallExpr)
	if !ok || len(constructor.TypeArgs) != 0 || len(constructor.NamedArgs) != 0 {
		return ClassDecl{}, nil, fmt.Errorf("%s expects Projection(row.field, ...) or the row parameter", method)
	}
	callee, ok := constructor.Callee.(IdentExpr)
	if !ok {
		return ClassDecl{}, nil, fmt.Errorf("%s projection must construct a local data class", method)
	}
	projection, ok := g.classes[callee.Name]
	if !ok || !projection.Data {
		return ClassDecl{}, nil, fmt.Errorf("%s projection type %s must be a data class", method, callee.Name)
	}
	if len(constructor.Args) != len(projection.Fields) {
		return ClassDecl{}, nil, fmt.Errorf("%s projection %s expects %d fields, got %d", method, projection.Name, len(projection.Fields), len(constructor.Args))
	}
	columns := make([]string, 0, len(constructor.Args))
	for i, arg := range constructor.Args {
		source, err := sqlRowField(arg, rowClass, rowName)
		if err != nil {
			return ClassDecl{}, nil, fmt.Errorf("%s projection argument %d: %w", method, i+1, err)
		}
		target := projection.Fields[i]
		if !sqlProjectionTypesCompatible(target.Type, source.Type) {
			return ClassDecl{}, nil, fmt.Errorf("%s projection field %s has type %s but row field %s has type %s", method, target.Name, target.Type, source.Name, source.Type)
		}
		columns = append(columns, sqlColumn(source))
	}
	return projection, columns, nil
}

func (g *goGenerator) sqlWhere(call CallExpr, class ClassDecl, placeholderStart int) (string, []string, error) {
	lambda, err := sqlLambdaArg(call, "where")
	if err != nil {
		return "", nil, err
	}
	rowName, body, err := sqlLambdaExpr(lambda, class, "where")
	if err != nil {
		return "", nil, err
	}
	predicate, args, err := g.sqlPredicate(body, class, rowName)
	if err != nil {
		return "", nil, err
	}
	return postgresPlaceholders(predicate, placeholderStart), args, nil
}

func sqlOrder(step sqlCallStep, class ClassDecl) (string, error) {
	lambda, err := sqlLambdaArg(step.call, step.name)
	if err != nil {
		return "", err
	}
	rowName, body, err := sqlLambdaExpr(lambda, class, step.name)
	if err != nil {
		return "", err
	}
	field, err := sqlRowField(body, class, rowName)
	if err != nil {
		return "", fmt.Errorf("%s: %w", step.name, err)
	}
	direction := ""
	if step.name == "orderByDescending" {
		direction = " DESC"
	}
	return sqlColumn(field) + direction, nil
}

func (g *goGenerator) sqlLimit(call CallExpr) (string, []string, error) {
	if len(call.Args) != 1 || len(call.NamedArgs) != 0 || len(call.TypeArgs) != 0 {
		return "", nil, fmt.Errorf("limit() expects exactly one Int argument")
	}
	if literal, ok := call.Args[0].(IntExpr); ok {
		value, err := strconv.Atoi(literal.Value)
		if err != nil || value < 0 {
			return "", nil, fmt.Errorf("limit() requires a non-negative Int")
		}
		return literal.Value, nil, nil
	}
	if unary, ok := call.Args[0].(UnaryExpr); ok && unary.Op == "-" {
		if _, ok := unary.Value.(IntExpr); ok {
			return "", nil, fmt.Errorf("limit() requires a non-negative Int")
		}
	}
	if typ := g.exprType(call.Args[0]); typ != "Int" {
		return "", nil, fmt.Errorf("limit() argument must have type Int, got %s", typ)
	}
	value, err := g.expr(call.Args[0], "Int")
	if err != nil {
		return "", nil, err
	}
	return "?", []string{value}, nil
}

func sqlNoArgs(call CallExpr) bool {
	return len(call.Args) == 0 && len(call.NamedArgs) == 0 && len(call.TypeArgs) == 0
}

func postgresPlaceholders(query string, start int) string {
	var out strings.Builder
	next := start
	for _, r := range query {
		if r == '?' {
			out.WriteString("$")
			out.WriteString(strconv.Itoa(next))
			next++
		} else {
			out.WriteRune(r)
		}
	}
	return out.String()
}

func sqlLambdaArg(call CallExpr, method string) (LambdaExpr, error) {
	if len(call.TypeArgs) != 0 || len(call.NamedArgs) != 0 || len(call.Args) != 1 {
		return LambdaExpr{}, fmt.Errorf("%s expects exactly one lambda", method)
	}
	lambda, ok := call.Args[0].(LambdaExpr)
	if !ok {
		return LambdaExpr{}, fmt.Errorf("%s expects a lambda", method)
	}
	return lambda, nil
}

func sqlLambdaExpr(lambda LambdaExpr, class ClassDecl, method string) (string, Expr, error) {
	rowName := "it"
	if !lambda.ImplicitIt {
		if len(lambda.Params) != 1 {
			return "", nil, fmt.Errorf("%s lambda expects one row parameter", method)
		}
		if lambda.Params[0].Type != "" && lambda.Params[0].Type != class.Name {
			return "", nil, fmt.Errorf("%s lambda parameter must have type %s", method, class.Name)
		}
		rowName = lambda.Params[0].Name
	}
	if len(lambda.Body) != 1 {
		return "", nil, fmt.Errorf("%s lambda must contain one expression", method)
	}
	stmt, ok := lambda.Body[0].(ExprStmt)
	if !ok {
		return "", nil, fmt.Errorf("%s lambda must contain one expression", method)
	}
	return rowName, stmt.Value, nil
}

func (g *goGenerator) sqlPredicate(expr Expr, class ClassDecl, rowName string) (string, []string, error) {
	switch e := expr.(type) {
	case BinaryExpr:
		if e.Op == "&&" || e.Op == "||" {
			left, leftArgs, err := g.sqlPredicate(e.Left, class, rowName)
			if err != nil {
				return "", nil, err
			}
			right, rightArgs, err := g.sqlPredicate(e.Right, class, rowName)
			if err != nil {
				return "", nil, err
			}
			op := "AND"
			if e.Op == "||" {
				op = "OR"
			}
			return "(" + left + " " + op + " " + right + ")", append(leftArgs, rightArgs...), nil
		}
		if !isSQLComparison(e.Op) {
			return "", nil, fmt.Errorf("unsupported SQL predicate operator %q", e.Op)
		}
		left, err := g.sqlOperand(e.Left, class, rowName)
		if err != nil {
			return "", nil, err
		}
		right, err := g.sqlOperand(e.Right, class, rowName)
		if err != nil {
			return "", nil, err
		}
		if left.typ == "Null" || right.typ == "Null" {
			if e.Op != "==" && e.Op != "!=" {
				return "", nil, fmt.Errorf("null only supports == and != in SQL predicates")
			}
			if left.typ == "Null" && right.typ == "Null" {
				return "", nil, fmt.Errorf("SQL predicate cannot compare null with null")
			}
			value := left
			if value.typ == "Null" {
				value = right
			}
			if !sqlNullableType(value.typ) {
				return "", nil, fmt.Errorf("SQL null comparison requires a nullable operand, got %s", value.typ)
			}
			op := "IS NULL"
			if e.Op == "!=" {
				op = "IS NOT NULL"
			}
			return value.sql + " " + op, value.args, nil
		}
		if !sqlTypesCompatible(left.typ, right.typ) {
			return "", nil, fmt.Errorf("SQL predicate compares incompatible types %s and %s", left.typ, right.typ)
		}
		if e.Op == ">" || e.Op == ">=" || e.Op == "<" || e.Op == "<=" {
			if !(sqlNumericType(left.typ) && sqlNumericType(right.typ)) && !(sqlTimestampType(left.typ) && sqlTimestampType(right.typ)) {
				return "", nil, fmt.Errorf("SQL ordering comparison requires numeric operands or timestamp operands, got %s and %s", left.typ, right.typ)
			}
		}
		op := map[string]string{"==": "=", "!=": "<>", ">": ">", ">=": ">=", "<": "<", "<=": "<="}[e.Op]
		return left.sql + " " + op + " " + right.sql, append(left.args, right.args...), nil
	case UnaryExpr:
		if e.Op != "!" {
			return "", nil, fmt.Errorf("unsupported SQL predicate unary operator %q", e.Op)
		}
		inner, args, err := g.sqlPredicate(e.Value, class, rowName)
		if err != nil {
			return "", nil, err
		}
		return "(NOT " + inner + ")", args, nil
	case SelectorExpr:
		field, err := sqlRowField(e, class, rowName)
		if err != nil {
			return "", nil, err
		}
		if field.Type != "Boolean" {
			return "", nil, fmt.Errorf("SQL predicate field %s has type %s, not Boolean", field.Name, field.Type)
		}
		return sqlColumn(field), nil, nil
	default:
		return "", nil, fmt.Errorf("SQL where lambda must produce a Boolean predicate")
	}
}

type sqlOperandValue struct {
	sql  string
	typ  string
	args []string
}

func (g *goGenerator) sqlOperand(expr Expr, class ClassDecl, rowName string) (sqlOperandValue, error) {
	if selector, ok := expr.(SelectorExpr); ok {
		if receiver, ok := selector.Receiver.(IdentExpr); ok && receiver.Name == rowName {
			field, err := sqlField(class, selector.Name)
			if err != nil {
				return sqlOperandValue{}, err
			}
			return sqlOperandValue{sql: sqlColumn(field), typ: field.Type}, nil
		}
	}
	if call, ok := expr.(CallExpr); ok {
		if ident, ok := call.Callee.(IdentExpr); ok && ident.Name == "now" {
			if !sqlNoArgs(call) {
				return sqlOperandValue{}, fmt.Errorf("now() does not accept arguments")
			}
			return sqlOperandValue{sql: "CURRENT_TIMESTAMP", typ: "time.Time"}, nil
		}
	}
	if binary, ok := expr.(BinaryExpr); ok && (binary.Op == "+" || binary.Op == "-") {
		left, err := g.sqlOperand(binary.Left, class, rowName)
		if err != nil {
			return sqlOperandValue{}, err
		}
		right, err := g.sqlOperand(binary.Right, class, rowName)
		if err != nil {
			return sqlOperandValue{}, err
		}
		if !sqlNumericType(left.typ) || !sqlNumericType(right.typ) {
			return sqlOperandValue{}, fmt.Errorf("SQL arithmetic requires numeric operands, got %s and %s", left.typ, right.typ)
		}
		return sqlOperandValue{sql: "(" + left.sql + " " + binary.Op + " " + right.sql + ")", typ: left.typ, args: append(left.args, right.args...)}, nil
	}
	typ := ""
	switch e := expr.(type) {
	case IntExpr:
		typ = "Int"
	case FloatExpr:
		typ = "Double"
	case StringExpr:
		typ = "String"
	case BoolExpr:
		typ = "Boolean"
	case NullExpr:
		return sqlOperandValue{sql: "NULL", typ: "Null"}, nil
	case UnaryExpr:
		if e.Op != "-" {
			return sqlOperandValue{}, fmt.Errorf("unsupported SQL value expression")
		}
		switch e.Value.(type) {
		case IntExpr:
			typ = "Int"
		case FloatExpr:
			typ = "Double"
		default:
			return sqlOperandValue{}, fmt.Errorf("SQL unary parameters only support numeric literals")
		}
	default:
		typ = g.exprType(expr)
	}
	if typ == "" {
		return sqlOperandValue{}, fmt.Errorf("SQL parameter has unknown type")
	}
	value, err := g.expr(expr, typ)
	if err != nil {
		return sqlOperandValue{}, err
	}
	return sqlOperandValue{sql: "?", typ: typ, args: []string{value}}, nil
}

func (g *goGenerator) sqlTypedUpdateAssignments(call CallExpr, class ClassDecl) ([]string, []string, error) {
	lambda, err := sqlLambdaArg(call, "set")
	if err != nil {
		return nil, nil, err
	}
	rowName := "it"
	if !lambda.ImplicitIt {
		if len(lambda.Params) != 1 {
			return nil, nil, fmt.Errorf("set lambda expects one row parameter")
		}
		if lambda.Params[0].Type != "" && lambda.Params[0].Type != class.Name {
			return nil, nil, fmt.Errorf("set lambda parameter must have type %s", class.Name)
		}
		rowName = lambda.Params[0].Name
	}
	if len(lambda.Body) == 0 {
		return nil, nil, fmt.Errorf("set lambda requires at least one set(row.field, value) expression")
	}
	var assignments, args []string
	seen := map[string]bool{}
	for _, stmt := range lambda.Body {
		exprStmt, ok := stmt.(ExprStmt)
		if !ok {
			return nil, nil, fmt.Errorf("set lambda only supports set(row.field, value) expressions")
		}
		setCall, ok := exprStmt.Value.(CallExpr)
		if !ok {
			return nil, nil, fmt.Errorf("set lambda only supports set(row.field, value) expressions")
		}
		callee, ok := setCall.Callee.(IdentExpr)
		if !ok || callee.Name != "set" || len(setCall.Args) != 2 || len(setCall.NamedArgs) != 0 || len(setCall.TypeArgs) != 0 {
			return nil, nil, fmt.Errorf("set lambda expects set(%s.field, value)", rowName)
		}
		target, err := sqlRowField(setCall.Args[0], class, rowName)
		if err != nil {
			return nil, nil, fmt.Errorf("set target: %w", err)
		}
		if !target.Mutable {
			return nil, nil, fmt.Errorf("set target %s is immutable", target.Name)
		}
		if seen[target.Name] {
			return nil, nil, fmt.Errorf("duplicate set target %s", target.Name)
		}
		value, err := g.sqlOperand(setCall.Args[1], class, rowName)
		if err != nil {
			return nil, nil, fmt.Errorf("set value for %s: %w", target.Name, err)
		}
		if value.typ == "Null" {
			if !sqlNullableType(target.Type) {
				return nil, nil, fmt.Errorf("set target %s has non-nullable type %s", target.Name, target.Type)
			}
		} else if !sqlAssignmentTypesCompatible(target.Type, value.typ) {
			return nil, nil, fmt.Errorf("set target %s has type %s but value has type %s", target.Name, target.Type, value.typ)
		}
		seen[target.Name] = true
		assignments = append(assignments, sqlColumn(target)+" = "+value.sql)
		args = append(args, value.args...)
	}
	return assignments, args, nil
}

func sqlConflictUpdateAssignments(lambda LambdaExpr, class ClassDecl) ([]string, error) {
	excludedName := "it"
	if !lambda.ImplicitIt {
		if len(lambda.Params) != 1 {
			return nil, fmt.Errorf("doUpdate lambda expects one excluded-row parameter")
		}
		if lambda.Params[0].Type != "" && lambda.Params[0].Type != class.Name {
			return nil, fmt.Errorf("doUpdate lambda parameter must have type %s", class.Name)
		}
		excludedName = lambda.Params[0].Name
	}
	if len(lambda.Body) == 0 {
		return nil, fmt.Errorf("doUpdate lambda requires at least one set() expression")
	}
	assignments := make([]string, 0, len(lambda.Body))
	seen := map[string]bool{}
	for _, stmt := range lambda.Body {
		exprStmt, ok := stmt.(ExprStmt)
		if !ok {
			return nil, fmt.Errorf("doUpdate only supports set() expressions")
		}
		call, ok := exprStmt.Value.(CallExpr)
		if !ok {
			return nil, fmt.Errorf("doUpdate only supports set() expressions")
		}
		callee, ok := call.Callee.(IdentExpr)
		if !ok || callee.Name != "set" || len(call.Args) != 2 || len(call.NamedArgs) != 0 || len(call.TypeArgs) != 0 {
			return nil, fmt.Errorf("doUpdate expects set(%s.field, %s.field)", class.Name, excludedName)
		}
		targetRef, ok := call.Args[0].(SelectorExpr)
		if !ok {
			return nil, fmt.Errorf("set target must be %s.field", class.Name)
		}
		targetType, ok := targetRef.Receiver.(IdentExpr)
		if !ok || targetType.Name != class.Name {
			return nil, fmt.Errorf("set target must be %s.field", class.Name)
		}
		target, err := sqlField(class, targetRef.Name)
		if err != nil {
			return nil, fmt.Errorf("set target: %w", err)
		}
		if !target.Mutable {
			return nil, fmt.Errorf("set target %s is immutable", target.Name)
		}
		if seen[target.Name] {
			return nil, fmt.Errorf("duplicate set target %s", target.Name)
		}
		sourceRef, ok := call.Args[1].(SelectorExpr)
		if !ok {
			return nil, fmt.Errorf("set value must be %s.field", excludedName)
		}
		sourceReceiver, ok := sourceRef.Receiver.(IdentExpr)
		if !ok || sourceReceiver.Name != excludedName {
			return nil, fmt.Errorf("set value must be %s.field", excludedName)
		}
		source, err := sqlField(class, sourceRef.Name)
		if err != nil {
			return nil, fmt.Errorf("set value: %w", err)
		}
		if !sqlAssignmentTypesCompatible(target.Type, source.Type) {
			return nil, fmt.Errorf("set target %s has type %s but excluded.%s has type %s", target.Name, target.Type, source.Name, source.Type)
		}
		seen[target.Name] = true
		assignments = append(assignments, sqlColumn(target)+" = EXCLUDED."+sqlColumn(source))
	}
	return assignments, nil
}

func sqlConflictFields(expr Expr, class ClassDecl, rowName string) ([]FieldDecl, error) {
	if call, ok := expr.(CallExpr); ok {
		callee, ok := call.Callee.(IdentExpr)
		if !ok || (callee.Name != "listOf" && callee.Name != "mutableListOf") || len(call.Args) == 0 || len(call.TypeArgs) != 0 || len(call.NamedArgs) != 0 {
			return nil, fmt.Errorf("onConflict expects a row field or listOf(row.field, ...)")
		}
		fields := make([]FieldDecl, 0, len(call.Args))
		seen := map[string]bool{}
		for _, arg := range call.Args {
			field, err := sqlRowField(arg, class, rowName)
			if err != nil {
				return nil, fmt.Errorf("onConflict: %w", err)
			}
			if seen[field.Name] {
				return nil, fmt.Errorf("onConflict contains duplicate field %s", field.Name)
			}
			seen[field.Name] = true
			fields = append(fields, field)
		}
		return fields, nil
	}
	field, err := sqlRowField(expr, class, rowName)
	if err != nil {
		return nil, fmt.Errorf("onConflict: %w", err)
	}
	return []FieldDecl{field}, nil
}

func sqlRowField(expr Expr, class ClassDecl, rowName string) (FieldDecl, error) {
	selector, ok := expr.(SelectorExpr)
	if !ok {
		return FieldDecl{}, fmt.Errorf("expected %s.field", rowName)
	}
	receiver, ok := selector.Receiver.(IdentExpr)
	if !ok || receiver.Name != rowName {
		return FieldDecl{}, fmt.Errorf("expected %s.field", rowName)
	}
	return sqlField(class, selector.Name)
}

func sqlField(class ClassDecl, name string) (FieldDecl, error) {
	for _, field := range class.Fields {
		if field.Name == name {
			return field, nil
		}
	}
	return FieldDecl{}, fmt.Errorf("SQL row class %s has no field %s", class.Name, name)
}

func sqlColumn(field FieldDecl) string {
	if field.Column != "" {
		return field.Column
	}
	return snakeCase(field.Name)
}

func sqlQueryValue(query string, args []string) string {
	return "GotlinSQLQuery{SQL: " + strconv.Quote(query) + ", Args: []any{" + strings.Join(args, ", ") + "}}"
}

func isSQLComparison(op string) bool {
	switch op {
	case "==", "!=", ">", ">=", "<", "<=":
		return true
	default:
		return false
	}
}

func sqlBaseType(typ string) string {
	return strings.TrimSuffix(typ, "?")
}

func sqlNullableType(typ string) bool {
	return strings.HasSuffix(typ, "?")
}

func sqlNumericType(typ string) bool {
	switch sqlBaseType(typ) {
	case "Int", "Float", "Double":
		return true
	default:
		return false
	}
}

func sqlTimestampType(typ string) bool {
	return sqlBaseType(typ) == "time.Time"
}

func sqlTypesCompatible(left, right string) bool {
	if left == "Null" || right == "Null" {
		return true
	}
	left = sqlBaseType(left)
	right = sqlBaseType(right)
	if left == right {
		return true
	}
	return sqlNumericType(left) && sqlNumericType(right)
}

func sqlProjectionTypesCompatible(target, source string) bool {
	return target == source
}

func sqlAssignmentTypesCompatible(target, source string) bool {
	if sqlBaseType(target) != sqlBaseType(source) {
		return false
	}
	return sqlNullableType(target) || !sqlNullableType(source)
}

func programContainsSQL(program *Program) bool {
	return programExprMatches(program, func(expr Expr) bool {
		_, _, _, ok := splitSQLChain(expr)
		return ok
	})
}

func programContainsSQLExecution(program *Program) bool {
	return programExprMatches(program, func(expr Expr) bool {
		_, _, steps, ok := splitSQLChain(expr)
		if !ok || len(steps) == 0 {
			return false
		}
		switch steps[len(steps)-1].name {
		case "fetch", "single", "iterator":
			return true
		default:
			return false
		}
	})
}

func exprMatches(expr Expr, match func(Expr) bool) bool {
	if match(expr) {
		return true
	}
	switch e := expr.(type) {
	case UnaryExpr:
		return exprMatches(e.Value, match)
	case BinaryExpr:
		return exprMatches(e.Left, match) || exprMatches(e.Right, match)
	case CallExpr:
		if exprMatches(e.Callee, match) {
			return true
		}
		for _, arg := range e.Args {
			if exprMatches(arg, match) {
				return true
			}
		}
		for _, arg := range e.NamedArgs {
			if exprMatches(arg.Value, match) {
				return true
			}
		}
	case SelectorExpr:
		return exprMatches(e.Receiver, match)
	case IndexExpr:
		return exprMatches(e.Receiver, match) || exprMatches(e.Index, match)
	case LambdaExpr:
		return stmtsMatch(e.Body, match)
	}
	return false
}

func stmtsMatch(stmts []Stmt, match func(Expr) bool) bool {
	for _, stmt := range stmts {
		switch s := stmt.(type) {
		case VarDecl:
			if exprMatches(s.Value, match) {
				return true
			}
		case MultiVarDecl:
			if exprMatches(s.Value, match) {
				return true
			}
		case AssignStmt:
			if exprMatches(s.Value, match) {
				return true
			}
		case AddAssignStmt:
			if exprMatches(s.Value, match) {
				return true
			}
		case MultiAssignStmt:
			if exprMatches(s.Value, match) {
				return true
			}
		case ReturnStmt:
			if s.Value != nil && exprMatches(s.Value, match) {
				return true
			}
		case ThrowStmt:
			if exprMatches(s.Value, match) {
				return true
			}
		case GoStmt:
			if exprMatches(s.Value, match) {
				return true
			}
		case DeferStmt:
			if exprMatches(s.Value, match) {
				return true
			}
		case ExprStmt:
			if exprMatches(s.Value, match) {
				return true
			}
		case IfStmt:
			if exprMatches(s.Cond, match) || stmtsMatch(s.Then, match) || stmtsMatch(s.Else, match) {
				return true
			}
		case WhileStmt:
			if exprMatches(s.Cond, match) || stmtsMatch(s.Body, match) {
				return true
			}
		case ForEachStmt:
			if exprMatches(s.Source, match) || stmtsMatch(s.Body, match) {
				return true
			}
		case SelectStmt:
			for _, c := range s.Cases {
				if exprMatches(c.Source, match) || stmtsMatch(c.Body, match) {
					return true
				}
			}
		case TryCatchStmt:
			if stmtsMatch(s.TryBody, match) || stmtsMatch(s.CatchBody, match) {
				return true
			}
		}
	}
	return false
}

func programExprMatches(program *Program, match func(Expr) bool) bool {
	for _, fn := range program.Functions {
		if stmtsMatch(fn.Body, match) {
			return true
		}
	}
	for _, class := range program.Classes {
		for _, fn := range class.Methods {
			if stmtsMatch(fn.Body, match) {
				return true
			}
		}
	}
	for _, worker := range program.Workers {
		for _, field := range worker.Fields {
			if exprMatches(field.Value, match) {
				return true
			}
		}
		for _, fn := range worker.Methods {
			if stmtsMatch(fn.Body, match) {
				return true
			}
		}
	}
	return false
}