/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.android.tools.lint.checks

import com.android.SdkConstants
import com.android.tools.lint.detector.api.Category
import com.android.tools.lint.detector.api.Implementation
import com.android.tools.lint.detector.api.Issue
import com.android.tools.lint.detector.api.LayoutDetector
import com.android.tools.lint.detector.api.Scope
import com.android.tools.lint.detector.api.Severity
import com.android.tools.lint.detector.api.XmlContext
import com.android.tools.lint.detector.api.isDataBindingExpression
import org.w3c.dom.Attr
import java.lang.Integer.min

class DataBindingDetector : LayoutDetector() {
    override fun getApplicableAttributes(): Collection<String> {
        return ALL
    }

    override fun visitAttribute(context: XmlContext, attribute: Attr) {
        val elementName = attribute.ownerElement.tagName
        val attributeName = attribute.name

        if (isDataBindingExpression(attribute.value) ||
            isVariableType(elementName, attributeName)
        ) {
            val rawText = context.getContents() ?: return
            val start = context.parser.getNodeStartOffset(context, attribute)
            if (start == -1) {
                return
            }
            val end = min(rawText.length, context.parser.getNodeEndOffset(context, attribute))
            var isContained = false
            for (index in start until end) {
                if (rawText[index] == '<') {
                    isContained = true
                    break
                }
            }

            if (isContained) {
                val fix = fix().name("Change '<' to '&lt;'")
                    .replace()
                    .text("<")
                    .with("&lt;")
                    .build()
                context.report(
                    ESCAPE_XML,
                    attribute,
                    context.getValueLocation(attribute),
                    "`<` must be escaped (as `&lt;`) in attribute values",
                    fix
                )
            }
        }
    }

    private fun isVariableType(elementName: String, attributeName: String): Boolean {
        return elementName == SdkConstants.TAG_VARIABLE && attributeName == SdkConstants.ATTR_TYPE
    }

    companion object {
        /** The main issue discovered by this detector */
        @JvmField
        val ESCAPE_XML = Issue.create(
            id = "XmlEscapeNeeded",
            briefDescription = "Missing XML Escape",
            explanation = """
              When a string contains characters that have special usage in XML, \
              you must escape the characters.
            """,
            category = Category.CORRECTNESS,
            priority = 5,
            severity = Severity.ERROR,
            implementation = Implementation(
                DataBindingDetector::class.java,
                Scope.RESOURCE_FILE_SCOPE
            )
        )
    }
}