package com.codechecker.cache.key;

import com.codechecker.cache.schema.SourceIndex;
import com.github.javaparser.ast.body.ClassOrInterfaceDeclaration;
import com.github.javaparser.ast.body.FieldDeclaration;
import com.github.javaparser.ast.body.MethodDeclaration;
import com.github.javaparser.ast.body.VariableDeclarator;
import com.github.javaparser.ast.expr.BinaryExpr;
import com.github.javaparser.ast.expr.Expression;
import com.github.javaparser.ast.expr.FieldAccessExpr;
import com.github.javaparser.ast.expr.MethodCallExpr;
import com.github.javaparser.ast.expr.NameExpr;
import com.github.javaparser.ast.expr.StringLiteralExpr;
import com.github.javaparser.ast.stmt.ReturnStmt;

import java.util.Optional;

/**
 * 尽力将 Redis key 表达式静态推断为一个「key 模式」，动态部分以 {@code *} 表示。
 */
public class RedisKeyResolver {

    private static final int MAX_DEPTH = 8;

    private final SourceIndex index;

    public RedisKeyResolver(SourceIndex index) {
        this.index = index;
    }

    public String resolve(Expression keyExpr, ClassOrInterfaceDeclaration enclosingClass,
                          SourceIndex.IndexedType context) {
        String raw = resolveExpr(keyExpr, enclosingClass, context, 0);
        return normalize(raw);
    }

    private String resolveExpr(Expression expr, ClassOrInterfaceDeclaration enclosingClass,
                               SourceIndex.IndexedType context, int depth) {
        if (expr == null || depth > MAX_DEPTH) {
            return "*";
        }
        if (expr instanceof StringLiteralExpr) {
            return ((StringLiteralExpr) expr).asString();
        }
        if (expr instanceof BinaryExpr) {
            BinaryExpr be = (BinaryExpr) expr;
            if (be.getOperator() == BinaryExpr.Operator.PLUS) {
                return resolveExpr(be.getLeft(), enclosingClass, context, depth + 1)
                        + resolveExpr(be.getRight(), enclosingClass, context, depth + 1);
            }
            return "*";
        }
        if (expr instanceof NameExpr) {
            String name = ((NameExpr) expr).getNameAsString();
            String constVal = lookupConstant(enclosingClass, name, context, depth);
            if (constVal != null) {
                return constVal;
            }
            String methodVal = lookupMethodReturn(enclosingClass, name, context, depth);
            return methodVal != null ? methodVal : "*";
        }
        if (expr instanceof FieldAccessExpr) {
            FieldAccessExpr fae = (FieldAccessExpr) expr;
            String fieldName = fae.getNameAsString();
            if (fae.getScope() instanceof NameExpr) {
                String scope = ((NameExpr) fae.getScope()).getNameAsString();
                String local = lookupConstant(enclosingClass, fieldName, context, depth);
                if (local != null && scope.equals(enclosingClass == null ? "" : enclosingClass.getNameAsString())) {
                    return local;
                }
                String external = lookupExternalConstant(scope, fieldName, context, depth);
                if (external != null) {
                    return external;
                }
            }
            String scope = fae.getScope().toString();
            String external = lookupExternalConstant(scope, fieldName, context, depth);
            if (external != null) {
                return external;
            }
            String local = lookupConstant(enclosingClass, fieldName, context, depth);
            return local != null ? local : "*";
        }
        if (expr instanceof MethodCallExpr) {
            MethodCallExpr call = (MethodCallExpr) expr;
            String name = call.getNameAsString();
            if ("format".equals(name) && !call.getArguments().isEmpty()) {
                String fmt = resolveExpr(call.getArgument(0), enclosingClass, context, depth + 1);
                return fmt.replaceAll("%[-0-9.]*[sdxDX]", "*");
            }
            String methodVal = lookupMethodReturn(enclosingClass, name, context, depth);
            return methodVal != null ? methodVal : "*";
        }
        return "*";
    }

    private String lookupConstant(ClassOrInterfaceDeclaration clazz, String name,
                                  SourceIndex.IndexedType context, int depth) {
        if (clazz == null) {
            return null;
        }
        for (FieldDeclaration field : clazz.getFields()) {
            if (!field.isStatic()) {
                continue;
            }
            for (VariableDeclarator var : field.getVariables()) {
                if (var.getNameAsString().equals(name)) {
                    Optional<Expression> init = var.getInitializer();
                    if (init.isPresent()) {
                        return resolveExpr(init.get(), clazz, context, depth + 1);
                    }
                }
            }
        }
        return null;
    }

    private String lookupExternalConstant(String scopeName, String fieldName,
                                          SourceIndex.IndexedType context, int depth) {
        String fqn = index.resolveFqn(scopeName, context);
        if (fqn == null) {
            return null;
        }
        SourceIndex.IndexedType type = index.get(fqn);
        if (type == null) {
            return null;
        }
        return lookupConstant(type.getDeclaration(), fieldName, type, depth);
    }

    private String lookupMethodReturn(ClassOrInterfaceDeclaration clazz, String methodName,
                                      SourceIndex.IndexedType context, int depth) {
        if (clazz == null || depth > MAX_DEPTH) {
            return null;
        }
        for (MethodDeclaration method : clazz.getMethods()) {
            if (method.getNameAsString().equals(methodName) && method.getBody().isPresent()) {
                for (ReturnStmt ret : method.getBody().get().findAll(ReturnStmt.class)) {
                    if (ret.getExpression().isPresent()) {
                        return resolveExpr(ret.getExpression().get(), clazz, context, depth + 1);
                    }
                }
            }
        }
        return null;
    }

    private String normalize(String raw) {
        if (raw == null || raw.isEmpty()) {
            return "unknown-key";
        }
        String collapsed = raw.replaceAll("\\*+", "*");
        if (collapsed.equals("*")) {
            return "unknown-key";
        }
        return collapsed;
    }
}