/**
 * Script for creating a changelog. Call:
 * ```
 * kotlin changelog.main.kts release/1.6.0 1.6.0-rc02
 * ```
 * where:
 * release/1.6.0 - the commit of the version
 * 1.6.0-rc02 - the name of the version
 *
 * It modifies CHANGELOG.md and adds new changes between the last version in CHANGELOG.md and the specified version.
 *
 * Changelog entries are generated from reading Release Notes in GitHub PR's.
 *
 * ## How to run Kotlin scripts
 * Option 1 - via Command line
 * 1. Download https://github.com/JetBrains/kotlin/releases/tag/v1.9.22 and add `bin` to PATH
 *
 * Option 2 - via IntelliJ:
 * 1. Right click on the script
 * 2. More Run/Debug
 * 3. Modify Run Configuration...
 * 4. Add Program arguments
 * 5. Clear all "Before launch" tasks (you can edit the system-wide template as well)
 * 6. OK
 */

@file:Repository("https://repo1.maven.org/maven2/")
@file:DependsOn("com.google.code.gson:gson:2.10.1")

import com.google.gson.Gson
import java.io.File
import java.io.IOException
import java.net.URL
import java.time.LocalDate
import java.time.format.DateTimeFormatter
import java.util.*
import java.util.concurrent.TimeUnit

//region ========================================== CONSTANTS =========================================

// Sections from the template https://github.com/JetBrains/compose-multiplatform/blob/master/.github/PULL_REQUEST_TEMPLATE.md?plain=1
// Changelog should contain only these categories

val standardSections = listOf(
    "Highlights",
    "Known Issues",
    "Breaking Changes",
    "Features",
    "Fixes",
)

val standardSubsections = listOf(
    "Multiple Platforms",
    "iOS",
    "Desktop",
    "Web",
    "Android",
    "Resources",
    "Gradle Plugin",
    "Lifecycle",
    "Navigation",
)

val changelogFile = __FILE__.resolve("../../CHANGELOG.md")

//endregion

val argsKeyless = args
    .filter { !it.contains("=") }

val argsKeyToValue = args
    .filter { it.contains("=") }
    .associate { it.substringBefore("=") to it.substringAfter("=") }

val versionCommit = argsKeyless.getOrNull(0) ?: "HEAD"
val versionName = argsKeyless.getOrNull(1) ?: versionCommit
val token = argsKeyToValue["token"]

println("Note. The script supports optional arguments: kotlin changelog.main.kts [versionCommit] [versionName] [token=githubToken]")
if (token == null) {
    println("To increase the rate limit, specify token (https://github.com/settings/tokens)")
}
println()

val currentChangelog = changelogFile.readText()
val previousChangelog =
    if (currentChangelog.startsWith("# $versionName ")) {
        val nextChangelogIndex = currentChangelog.indexOf("\n# ")
        currentChangelog.substring(nextChangelogIndex).removePrefix("\n")
    } else {
        currentChangelog
    }

val previousVersion = previousChangelog.substringAfter("# ").substringBefore(" (")

println("Generating changelog between $previousVersion and $versionName")

val newChangelog = getChangelog("v$previousVersion", versionCommit, previousVersion, versionName)

changelogFile.writeText(
    newChangelog + previousChangelog
)

println()
println("CHANGELOG.md changed")


fun getChangelog(firstCommit: String, lastCommit: String, firstVersion: String, lastVersion: String): String {
    val entries = entriesForRepo("JetBrains/compose-multiplatform-core", firstCommit, lastCommit) +
            entriesForRepo("JetBrains/compose-multiplatform", firstCommit, lastCommit)

    return buildString {
        appendLine("# $lastVersion (${currentChangelogDate()})")

        appendLine()
        appendLine("_Changes since ${firstVersion}_")
        appendLine()

        entries
            .sortedBy { it.sectionOrder() }
            .groupBy { it.sectionName() }
            .forEach { (section, sectionEntries) ->
                appendLine("## $section")
                appendLine()

                sectionEntries
                    .sortedBy { it.subsectionOrder() }
                    .groupBy { it.subsectionName() }
                    .forEach { (subsection, subsectionEntries) ->
                        appendLine("### $subsection")
                        appendLine()
                        subsectionEntries.forEach {
                            appendLine(it.format())
                        }
                        appendLine()
                    }
            }

        append(
            """
                ## Dependencies
        
                - Gradle Plugin `org.jetbrains.compose`, version `$lastVersion`. Based on Jetpack Compose libraries:
                  - [Runtime REDIRECT_PLACEHOLDER](https://developer.android.com/jetpack/androidx/releases/compose-runtime#REDIRECT_PLACEHOLDER)
                  - [UI REDIRECT_PLACEHOLDER](https://developer.android.com/jetpack/androidx/releases/compose-ui#REDIRECT_PLACEHOLDER)
                  - [Foundation REDIRECT_PLACEHOLDER](https://developer.android.com/jetpack/androidx/releases/compose-foundation#REDIRECT_PLACEHOLDER)
                  - [Material REDIRECT_PLACEHOLDER](https://developer.android.com/jetpack/androidx/releases/compose-material#REDIRECT_PLACEHOLDER)
                  - [Material3 REDIRECT_PLACEHOLDER](https://developer.android.com/jetpack/androidx/releases/compose-material3#REDIRECT_PLACEHOLDER)
        
                - Lifecycle libraries `org.jetbrains.androidx.lifecycle:lifecycle-*:RELEASE_PLACEHOLDER`. Based on [Jetpack Lifecycle REDIRECT_PLACEHOLDER](https://developer.android.com/jetpack/androidx/releases/lifecycle#REDIRECT_PLACEHOLDER)
                - Navigation libraries `org.jetbrains.androidx.navigation:navigation-*:RELEASE_PLACEHOLDER`. Based on [Jetpack Navigation REDIRECT_PLACEHOLDER](https://developer.android.com/jetpack/androidx/releases/navigation#REDIRECT_PLACEHOLDER)
                - Material3 Adaptive libraries `org.jetbrains.compose.material3.adaptive:adaptive*:RELEASE_PLACEHOLDER`. Based on [Jetpack Material3 Adaptive REDIRECT_PLACEHOLDER](https://developer.android.com/jetpack/androidx/releases/compose-material3-adaptive#REDIRECT_PLACEHOLDER)
        
                ---
            """.trimIndent()
        )

        appendLine()
        appendLine()

        val nonstandardSections = entries.mapNotNull { it.section }.toSet() - standardSections
        val nonstandardSubsections = entries.mapNotNull { it.subsection }.toSet() - standardSubsections

        if (nonstandardSections.isNotEmpty()) {
            println()
            println("WARNING! Changelog contains nonstandard sections. Please change them to the standard ones, or enhance the list in the PR template. List:\n${nonstandardSections.joinToString("\n")}")
        }

        if (nonstandardSubsections.isNotEmpty()) {
            println()
            println("WARNING! Changelog contains nonstandard subsections. Please change them to the standard ones, or enhance the list in the PR template. List:\n${nonstandardSubsections.joinToString("\n")}")
        }
    }
}

/**
 * September 2024
 */
fun currentChangelogDate() = LocalDate.now().format(DateTimeFormatter.ofPattern("MMMM yyyy", Locale.ENGLISH))

/**
 * Formats:
 * - A new approach to implementation of `platformLayers`. Now extra layers (such as Dialogs and Popups) drawing is merged into a single screen size canvas.
 *
 * to:
 * - [A new approach to implementation of `platformLayers`](link). Now extra layers (such as Dialogs and Popups) drawing is merged into a single screen size canvas.
 */
fun ChangelogEntry.format(): String {
    return if (link != null) {
        val linkStartIndex = maxOf(
            message.indexOfFirst { !it.isWhitespace() && it != '-' }.ifNegative { 0 },
            message.endIndexOf("_(prerelease fix)_ ").ifNegative { 0 },
            message.endIndexOf("(prerelease fix) ").ifNegative { 0 },
        )
        val linkLastIndex = message.indexOfAny(listOf(". ", " (")).ifNegative { message.length }

        val beforeLink = message.substring(0, linkStartIndex)
        val inLink = message.substring(linkStartIndex, linkLastIndex).removeLinks()
        val afterLink = message.substring(linkLastIndex, message.length)

        "$beforeLink[$inLink]($link)$afterLink"
    } else {
        message
    }
}

fun Int.ifNegative(value: () -> Int): Int = if (this < 0) value() else this

fun String.endIndexOf(value: String): Int = indexOf(value).let {
    if (it >= 0) {
        it + value.length
    } else {
        it
    }
}

/**
 * Converts:
 * Message (title)[some link], message
 *
 * to:
 * Message title, message
 */
fun String.removeLinks(): String = replace(Regex("\\[([^)]*)\\]\\([^\\]]*\\)"), "$1")

/**
 * Extract by format https://github.com/JetBrains/compose-multiplatform/blob/master/.github/PULL_REQUEST_TEMPLATE.md?plain=1
 */
fun GitHubPullEntry.extractReleaseNotes(link: String): List<ChangelogEntry> {
    // extract body inside "## Release Notes"
    val relNoteBody = run {
        val after = body?.substringAfter("## Release Notes", "")?.ifBlank { null }
            ?: body?.substringAfter("## Release notes", "")?.ifBlank { null } ?: body?.substringAfter(
                "## RelNote",
                ""
            )?.ifBlank { null }

        val before = after?.substringBefore("\n## ", "")?.ifBlank { null } ?: after?.substringBefore("\n# ", "")
            ?.ifBlank { null } ?: after

        before?.trim()
    }

    val list = mutableListOf<ChangelogEntry>()
    var section: String? = null
    var subsection: String? = null

    for (line in relNoteBody.orEmpty().split("\n")) {
        // parse "### Section - Subsection"
        if (line.startsWith("### ")) {
            val s = line.removePrefix("### ")
            section = s.substringBefore("-", "").trim().normalizeSectionName().ifEmpty { null }
            subsection = s.substringAfter("-", "").trim().normalizeSubsectionName().ifEmpty { null }
        } else if (section != null && line.isNotBlank()) {
            val isTopLevel = line.startsWith("-")
            val trimmedLine = line.trimEnd().removeSuffix(".")
            list.add(
                ChangelogEntry(
                    trimmedLine,
                    section,
                    subsection,
                    link.takeIf { isTopLevel }
                )
            )
        }
    }

    return list
}

/**
 * @param repo Example:
 *        JetBrains/compose-multiplatform-core
 */
fun entriesForRepo(repo: String, firstCommit: String, lastCommit: String): List<ChangelogEntry> {
    val pulls = (1..5)
        .flatMap {
            request<Array<GitHubPullEntry>>("https://api.github.com/repos/$repo/pulls?state=closed&per_page=100&page=$it").toList()
        }

    val pullNumberToPull = pulls.associateBy { it.number }
    val pullTitleToPull = pulls.associateBy { it.title }

    fun prForCommit(commit: GitHubCompareResponse.CommitEntry): GitHubPullEntry? {
        val (repoTitle, repoNumber) = repoTitleAndNumberForCommit(commit)
        return repoNumber?.let(pullNumberToPull::get) ?: pullTitleToPull[repoTitle]
    }

    fun changelogEntriesFor(
        pullRequest: GitHubPullEntry?
    ): List<ChangelogEntry> {
        return if (pullRequest != null) {
            val prTitle = pullRequest.title
            val prNumber = pullRequest.number
            val prLink = "https://github.com/$repo/pull/$prNumber"
            val prList = pullRequest.extractReleaseNotes(prLink)
            val changelogMessage = "- $prTitle"
            prList.ifEmpty {
                listOf(ChangelogEntry(changelogMessage, null, null, prLink))
            }
        } else {
            listOf()
        }
    }

    class CommitsResult(val commits: List<GitHubCompareResponse.CommitEntry>, val mergeBaseSha: String)

    fun fetchCommits(firsCommitSha: String, lastCommitSha: String): CommitsResult {
        lateinit var mergeBaseCommit: String
        val commits = fetchPagedUntilEmpty { page ->
            val result =
                request<GitHubCompareResponse>("https://api.github.com/repos/$repo/compare/$firsCommitSha...$lastCommitSha?per_page=1000&page=$page")
            mergeBaseCommit = result.merge_base_commit.sha
            result.commits
        }
        return CommitsResult(commits, mergeBaseCommit)
    }

    val main = fetchCommits(firstCommit, lastCommit)
    val previous = fetchCommits(main.mergeBaseSha, firstCommit)
    val pullRequests = main.commits.mapNotNull { prForCommit(it) }.toSet()
    val previousVersionPullRequests = previous.commits.mapNotNull { prForCommit(it) }.toSet()
    return (pullRequests - previousVersionPullRequests).flatMap { changelogEntriesFor(it) }
}

/**
 * Extract the PR number from the commit.
 */
fun repoTitleAndNumberForCommit(commit: GitHubCompareResponse.CommitEntry): Pair<String, Int?> {
    val commitTitle = commit.commit.message.substringBefore("\n")
    // check title similar to `Fix import android flavors with compose resources (#4319)`
    val title = commitTitle.substringBeforeLast(" (#")
    val number = commitTitle.substringAfterLast(" (#").substringBefore(")").toIntOrNull()
    return title to number
}

data class ChangelogEntry(
    val message: String,
    val section: String?,
    val subsection: String?,
    val link: String?,
)

fun ChangelogEntry.sectionOrder(): Int = section?.let(standardSections::indexOf) ?: standardSections.size
fun ChangelogEntry.subsectionOrder(): Int = subsection?.let(standardSubsections::indexOf) ?: standardSubsections.size
fun ChangelogEntry.sectionName(): String = section ?: "Unknown"
fun ChangelogEntry.subsectionName(): String = subsection ?: "Unknown"
fun String.normalizeSectionName() = standardSections.find { it.lowercase() == this.lowercase() } ?: this
fun String.normalizeSubsectionName() = standardSubsections.find { it.lowercase() == this.lowercase() } ?: this

// example https://api.github.com/repos/JetBrains/compose-multiplatform-core/compare/v1.6.0-rc02...release/1.6.0
data class GitHubCompareResponse(val commits: List<CommitEntry>, val merge_base_commit: CommitEntry) {
    data class CommitEntry(val sha: String, val commit: Commit)
    data class Commit(val message: String)
}

// example https://api.github.com/repos/JetBrains/compose-multiplatform-core/pulls?state=closed
data class GitHubPullEntry(val number: Int, val title: String, val body: String?, val labels: List<Label>) {
    class Label(val name: String)
}

//region ========================================== UTILS =========================================

// from https://stackoverflow.com/a/41495542
fun String.runCommand(workingDir: File = File(".")) {
    ProcessBuilder(*split(" ").toTypedArray())
        .directory(workingDir)
        .redirectOutput(ProcessBuilder.Redirect.INHERIT)
        .redirectError(ProcessBuilder.Redirect.INHERIT)
        .start()
        .waitFor(5, TimeUnit.MINUTES)
}

fun String.execCommand(workingDir: File = File(".")): String? {
    try {
        val parts = this.split("\\s".toRegex())
        val proc = ProcessBuilder(*parts.toTypedArray())
            .directory(workingDir)
            .redirectOutput(ProcessBuilder.Redirect.PIPE)
            .redirectError(ProcessBuilder.Redirect.PIPE)
            .start()

        proc.waitFor(60, TimeUnit.MINUTES)
        return proc.inputStream.bufferedReader().readText()
    } catch (e: IOException) {
        e.printStackTrace()
        return null
    }
}

inline fun <reified T> request(
    url: String
): T = exponentialRetry {
    println("Request $url")
    val connection = URL(url).openConnection()
    connection.setRequestProperty("User-Agent", "Compose-Multiplatform-Script")
    if (token != null) {
        connection.setRequestProperty("Authorization", "Bearer $token")
    }
    connection.getInputStream().use {
        Gson().fromJson(
            it.bufferedReader(),
            T::class.java
        )
    }
}

fun <T> exponentialRetry(block: () -> T): T {
    val exception = IOException()
    val retriesMinutes = listOf(1, 5, 15, 30, 60)
    for (retriesMinute in retriesMinutes) {
        try {
            return block()
        } catch (e: IOException) {
            e.printStackTrace()
            exception.addSuppressed(e)
            println("Retry in $retriesMinute minutes")
            Thread.sleep(retriesMinute.toLong() * 60 * 1000)
        }
    }
    throw exception
}

inline fun <T> fetchPagedUntilEmpty(fetch: (page: Int) -> List<T>): MutableList<T> {
    val all = mutableListOf<T>()
    var page = 1
    do {
        val result = fetch(page++)
        all.addAll(result)
    } while (result.isNotEmpty())
    return all
}

//endregion