/*
 * Copyright (C) 2012 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.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.Location
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 org.w3c.dom.Document

/**
 * Checks that the line endings in DOS files are consistent
 */
/** Constructs a new [DosLineEndingDetector]  */
class DosLineEndingDetector : LayoutDetector() {
    companion object Issues {
        /** Detects mangled DOS line ending documents  */
        @JvmField
        val ISSUE = Issue.create(
            id = "MangledCRLF",
            briefDescription = "Mangled file line endings",
            explanation = """
            On Windows, line endings are typically recorded as carriage return plus newline: \\r\\n.

            This detector looks for invalid line endings with repeated carriage return characters \
            (without newlines). Previous versions of the ADT plugin could accidentally introduce these \
            into the file, and when editing the file, the editor could produce confusing visual artifacts.
            """,
            moreInfo = "https://bugs.eclipse.org/bugs/show_bug.cgi?id=375421",
            category = Category.CORRECTNESS,
            priority = 2,
            severity = Severity.ERROR,
            // This check is probably not relevant for most users anymore
            enabledByDefault = false,
            implementation = Implementation(
                DosLineEndingDetector::class.java,
                Scope.RESOURCE_FILE_SCOPE
            )
        )
    }

    override fun visitDocument(context: XmlContext, document: Document) {
        val contents = context.getContents() ?: return

        // We could look for *consistency* and complain if you mix \n and \r\n too,
        // but that isn't really a problem (most editors handle it) so let's
        // not complain needlessly.

        var prev: Char = 0.toChar()
        var i = 0
        val n = contents.length
        while (i < n) {
            val c = contents[i]
            if (c == '\r' && prev == '\r') {
                val message =
                    "Incorrect line ending: found carriage return (`\\r`) without corresponding newline (`\\n`)"

                // Mark the whole line as the error range, since pointing just to the
                // line ending makes the error invisible in IDEs and error reports etc
                // Find the most recent non-blank line
                var blankLine = true
                for (index in i - 2 until i) {
                    val d = contents[index]
                    if (!Character.isWhitespace(d)) {
                        blankLine = false
                    }
                }

                var lineBegin = i
                for (index in i - 2 downTo 0) {
                    val d = contents[index]
                    if (d == '\n') {
                        lineBegin = index + 1
                        if (!blankLine) {
                            break
                        }
                    } else if (!Character.isWhitespace(d)) {
                        blankLine = false
                    }
                }

                val lineEnd = Math.min(contents.length, i + 1)
                val location = Location.create(context.file, contents, lineBegin, lineEnd)
                context.report(ISSUE, document.documentElement, location, message)
                return
            }
            prev = c
            i++
        }
    }
}