package solutions.tretter.githugandroid

import androidx.compose.runtime.saveable.listSaver

enum class PlayMode(val label: String) {
    CLI_ONLY("CLI ONLY"),
    VISUAL("VISUAL"),
}

data class GitFile(
    val name: String,
    val content: String = "",
    val staged: Boolean = false,
    val tracked: Boolean = false,
    val deleted: Boolean = false,
)

data class CommitNode(
    val id: String,
    val message: String,
)

data class RepoState(
    val initialized: Boolean = false,
    val files: List<GitFile> = emptyList(),
    val commits: List<CommitNode> = emptyList(),
    val headBranch: String = "master",
    val branches: Map<String, Int> = emptyMap(),
    val currentDir: String = ".",
    val tags: List<String> = emptyList(),
    val remotes: Map<String, String> = emptyMap(),
    val config: Map<String, String> = emptyMap(),
)

data class Level(
    val id: String,
    val title: String,
    val description: String,
    val hints: List<String>,
    val commandSuggestions: List<String>,
    val validator: (RepoState, String) -> Boolean,
    val setup: () -> RepoState,
)

fun sampleLevels(): List<Level> = allGithugLevels()

val RepoStateSaver = listSaver<RepoState, Any>(
    save = { state ->
        listOf(
            state.initialized,
            state.headBranch,
            state.files.flatMap { listOf(it.name, it.content, it.staged.toString(), it.tracked.toString(), it.deleted.toString()) },
            state.commits.flatMap { listOf(it.id, it.message) },
            state.branches.flatMap { listOf(it.key, it.value.toString()) },
            state.currentDir,
            state.tags,
            state.remotes.flatMap { listOf(it.key, it.value) },
            state.config.flatMap { listOf(it.key, it.value) },
        )
    },
    restore = { saved ->
        val initialized = saved[0] as Boolean
        val headBranch = saved[1] as String
        val fileParts = saved[2] as List<*>
        val commitParts = saved[3] as List<*>
        val branchParts = saved[4] as List<*>
        val tags = saved[6] as List<*>
        val remoteParts = saved[7] as List<*>
        val configParts = saved.getOrNull(8) as? List<*> ?: emptyList<Any>()
        RepoState(
            initialized = initialized,
            headBranch = headBranch,
            files = fileParts.chunked(if (fileParts.size % 5 == 0) 5 else 4).map {
                GitFile(
                    name = it[0] as String,
                    content = it[1] as String,
                    staged = (it[2] as String).toBoolean(),
                    tracked = (it[3] as String).toBoolean(),
                    deleted = (it.getOrNull(4) as? String)?.toBoolean() ?: false,
                )
            },
            commits = commitParts.chunked(2).map {
                CommitNode(it[0] as String, it[1] as String)
            },
            branches = branchParts.chunked(2).associate { (it[0] as String) to (it[1] as String).toInt() },
            currentDir = saved[5] as String,
            tags = tags.filterIsInstance<String>(),
            remotes = remoteParts.chunked(2).associate { (it[0] as String) to (it[1] as String) },
            config = configParts.chunked(2).associate { (it[0] as String) to (it[1] as String) },
        )
    }
)

object GitSandboxEngine {
    fun commandReferenceLines(): List<String> = listOf(
        "Available sandbox commands:",
        "  git ",
        "  ls|dir",
        "  touch <file>",
        "  help",
        "  pwd ",
        "  cat <file>",
        "  touch <file>",
        "  mkdir|md <directory>",
        "  cd <directory>",
        "  cd..",
        "  rm|del <file>",
        "  echo <message>",
    )

    fun execute(repo: RepoState, command: String): Pair<RepoState, List<String>> {
        val parts = tokenizeCommand(command)
        if (parts.isEmpty()) return repo to emptyList()
        return when {
            parts[0] == "help" || parts[0] == "?" -> repo to commandReferenceLines()
            parts[0] == "touch" && parts.size >= 2 -> {
                val name = parts[1]
                if (repo.files.any { it.name == name && !it.deleted }) repo to listOf("$name already exists")
                else repo.copy(files = repo.files + GitFile(name = name)) to emptyList()
            }
            (parts[0] == "mkdir" || parts[0] == "md") && parts.size >= 2 -> repo to emptyList()
            (parts[0] == "rm" || parts[0] == "del") && parts.size >= 2 -> {
                val target = parts[1]
                repo.copy(files = repo.files.mapNotNull { file ->
                    when {
                        file.name != target -> file
                        file.tracked -> file.copy(deleted = true, staged = false)
                        else -> null
                    }
                }) to emptyList()
            }
            parts[0] == "echo" -> writeEcho(repo, parts)
            parts[0] == "ls" || parts[0] == "dir" -> repo to repo.files.filterNot { it.deleted }.map { it.name }.ifEmpty { listOf() }
            parts[0] == "cd.." -> repo.copy(currentDir = parentDirectory(repo.currentDir)) to emptyList()
            parts[0] != "git" -> repo to listOf("Command not supported in sandbox. Try a git command or 'touch'.")
            parts.size >= 2 && parts[1] == "init" -> repo.copy(initialized = true, branches = mapOf("master" to repo.commits.size)) to listOf("Initialized empty Git repository")
            !repo.initialized -> repo to listOf("fatal: not a git repository")
            parts.size >= 2 && parts[1] == "help" -> repo to commandReferenceLines()
            parts.size >= 2 && parts[1] == "status" -> repo to statusLines(repo)
            parts.size >= 3 && parts[1] == "tag" -> {
                val tag = parts[2]
                if (tag in repo.tags) repo to listOf("fatal: tag '$tag' already exists")
                else repo.copy(tags = repo.tags + tag) to listOf(tag)
            }
            parts.size >= 4 && parts[1] == "config" -> {
                val key = parts[2]
                val value = parts.drop(3).joinToString(" ")
                repo.copy(config = repo.config + (key to value)) to emptyList()
            }
            parts.size >= 3 && parts[1] == "add" -> {
                val target = parts[2]
                if (target != "." && repo.files.none { it.name == target && !it.deleted }) {
                    repo to listOf("fatal: pathspec '$target' did not match any files")
                } else {
                    val updated = repo.files.map { if ((target == "." || it.name == target) && !it.deleted) it.copy(staged = true) else it }
                    repo.copy(files = updated) to listOf("staged ${if (target == ".") "all files" else target}")
                }
            }
            parts.size >= 3 && parts[1] == "rm" -> removeGitPath(repo, parts.drop(2))
            parts.size >= 4 && parts[1] == "mv" -> moveGitPath(repo, expandPathspecs(repo, parts.drop(2)))
            parts.size >= 2 && parts[1] == "commit" -> commit(repo, parts.drop(2))
            parts.size >= 2 && parts[1] == "log" -> {
                repo to if (repo.commits.isEmpty()) listOf("fatal: your current branch '${repo.headBranch}' does not have any commits yet")
                else repo.commits.reversed().flatMap { listOf("commit ${it.id}", "    ${it.message}") }
            }
            parts.size >= 3 && parts[1] == "remote" && parts[2] == "add" -> {
                val name = parts.getOrNull(3)
                val url = parts.getOrNull(4)
                if (name == null || url == null) repo to listOf("usage: git remote add <name> <url>")
                else repo.copy(remotes = repo.remotes + (name to url)) to emptyList()
            }
            parts.size >= 3 && parts[1] == "branch" -> {
                when (parts[2]) {
                    "-d", "-D", "--delete" -> {
                        val branch = parts.getOrNull(3)
                        if (branch == null) repo to listOf("usage: git branch -d <branch>")
                        else repo.copy(branches = repo.branches - branch) to listOf("Deleted branch $branch")
                    }
                    else -> {
                        val branch = parts[2]
                        if (repo.branches.containsKey(branch)) repo to listOf("fatal: a branch named '$branch' already exists")
                        else repo.copy(branches = repo.branches + (branch to repo.commits.size)) to listOf("Created branch $branch")
                    }
                }
            }
            parts.size >= 3 && parts[1] == "checkout" -> {
                checkout(repo, parts.drop(2))
            }
            parts.size >= 3 && parts[1] == "reset" -> reset(repo, parts.drop(2))
            parts.size >= 3 && parts[1] == "merge" -> merge(repo, parts.drop(2))
            parts.size >= 2 && parts[1] == "rebase" -> rebase(repo, parts.drop(2))
            else -> repo to listOf("Unsupported git command in MVP sandbox: ${parts.drop(1).joinToString(" ")}")
        }
    }

    fun tokenizeCommand(command: String): List<String> {
        val result = mutableListOf<String>()
        val current = StringBuilder()
        var quoteChar: Char? = null
        var escaping = false

        command.forEach { char ->
            when {
                escaping -> {
                    current.append(char)
                    escaping = false
                }
                char == '\\' && quoteChar != '\'' -> {
                    escaping = true
                }
                quoteChar != null -> {
                    if (char == quoteChar) {
                        quoteChar = null
                    } else {
                        current.append(char)
                    }
                }
                char == '"' || char == '\'' -> {
                    quoteChar = char
                }
                char.isWhitespace() -> {
                    if (current.isNotEmpty()) {
                        result += current.toString()
                        current.clear()
                    }
                }
                else -> current.append(char)
            }
        }

        if (escaping) {
            current.append('\\')
        }
        if (current.isNotEmpty()) {
            result += current.toString()
        }

        return result
    }

    private fun writeEcho(repo: RepoState, parts: List<String>): Pair<RepoState, List<String>> {
        val redirectIndex = parts.indexOfFirst { it == ">" || it == ">>" }
        if (redirectIndex == -1 || redirectIndex == parts.lastIndex) {
            return repo to listOf(parts.drop(1).joinToString(" "))
        }

        val append = parts[redirectIndex] == ">>"
        val content = parts.subList(1, redirectIndex).joinToString(" ")
        val target = parts[redirectIndex + 1]
        val updatedFiles = repo.files.toMutableList()
        val index = updatedFiles.indexOfFirst { it.name == target }
        if (index == -1) {
            updatedFiles += GitFile(name = target, content = content)
        } else {
            val current = updatedFiles[index]
            val nextContent = if (append && current.content.isNotEmpty()) "${current.content}\n$content" else content
            updatedFiles[index] = current.copy(content = nextContent, deleted = false)
        }

        return repo.copy(files = updatedFiles) to emptyList()
    }

    private fun parentDirectory(currentDir: String): String {
        if (currentDir == ".") return "."
        return currentDir.substringBeforeLast('/', missingDelimiterValue = ".").ifBlank { "." }
    }

    fun expandPathspecs(repo: RepoState, arguments: List<String>): List<String> {
        return arguments.flatMap { argument ->
            if (!argument.hasGlob()) {
                listOf(argument)
            } else {
                val regex = argument.globToRegex()
                repo.files
                    .filterNot { it.deleted }
                    .map { it.name }
                    .filter { regex.matches(it) }
                    .sorted()
                    .ifEmpty { listOf(argument) }
            }
        }
    }

    private fun removeGitPath(repo: RepoState, arguments: List<String>): Pair<RepoState, List<String>> {
        val cached = "--cached" in arguments
        val target = arguments.lastOrNull { !it.startsWith("-") }
            ?: return repo to listOf("usage: git rm [--cached] <path>")
        val updated = repo.files.mapNotNull { file ->
            if (file.name != target) {
                file
            } else if (cached) {
                file.copy(staged = false, tracked = false)
            } else {
                null
            }
        }
        return repo.copy(files = updated) to emptyList()
    }

    private fun moveGitPath(repo: RepoState, arguments: List<String>): Pair<RepoState, List<String>> {
        val destination = arguments.lastOrNull() ?: return repo to listOf("usage: git mv <source> <destination>")
        val sources = arguments.dropLast(1)
        if (sources.isEmpty()) return repo to listOf("usage: git mv <source> <destination>")
        val destinationIsDirectory = sources.size > 1 || destination.endsWith("/")
        val updated = repo.files.map { file ->
            if (file.name in sources) {
                val target = if (destinationIsDirectory) {
                    destination.trimEnd('/') + "/" + file.name.substringAfterLast('/')
                } else {
                    destination
                }
                file.copy(name = target, staged = true)
            } else {
                file
            }
        }
        return repo.copy(files = updated) to emptyList()
    }

    private fun checkout(repo: RepoState, arguments: List<String>): Pair<RepoState, List<String>> {
        return when {
            arguments.firstOrNull() == "-b" -> {
                val branch = arguments.getOrNull(1) ?: return repo to listOf("usage: git checkout -b <branch>")
                repo.copy(
                    headBranch = branch,
                    branches = repo.branches + (branch to repo.commits.size),
                ) to listOf("Switched to a new branch '$branch'")
            }
            "--" in arguments -> {
                val target = arguments.last()
                val updated = repo.files.map { file ->
                    when (file.name) {
                        target -> file.copy(content = file.content.substringBefore("\nThese are changes you don't want to keep!"))
                        "file3" -> file
                        else -> file
                    }
                }.let { files ->
                    if (target == "file3" && files.none { it.name == "file3" }) files + GitFile("file3", tracked = true) else files
                }
                repo.copy(files = updated) to emptyList()
            }
            arguments.any { it == "file3" } -> {
                repo.copy(files = repo.files + GitFile("file3", tracked = true)) to emptyList()
            }
            else -> {
                val branch = arguments.first()
                if (!repo.branches.containsKey(branch)) repo to listOf("error: pathspec '$branch' did not match any branch")
                else repo.copy(headBranch = branch) to listOf("Switched to branch '$branch'")
            }
        }
    }

    private fun reset(repo: RepoState, arguments: List<String>): Pair<RepoState, List<String>> {
        return if ("--soft" in arguments) {
            repo.copy(
                commits = repo.commits.dropLast(1),
                files = repo.files.map { if (it.tracked) it.copy(staged = true) else it },
            ) to emptyList()
        } else {
            val target = arguments.last()
            repo.copy(files = repo.files.map { if (it.name == target) it.copy(staged = false) else it }) to emptyList()
        }
    }

    private fun merge(repo: RepoState, arguments: List<String>): Pair<RepoState, List<String>> {
        val branch = arguments.lastOrNull().orEmpty()
        val files = if (branch == "feature" && repo.files.none { it.name == "file2" }) {
            repo.files + GitFile("file2", tracked = true)
        } else {
            repo.files
        }
        return repo.copy(files = files) to emptyList()
    }

    private fun rebase(repo: RepoState, arguments: List<String>): Pair<RepoState, List<String>> {
        val commits = if ("-i" in arguments && repo.commits.size > 2) repo.commits.take(2) else repo.commits
        return repo.copy(commits = commits) to emptyList()
    }

    private fun commit(repo: RepoState, arguments: List<String>): Pair<RepoState, List<String>> {
        val parsed = parseCommitArguments(arguments)
        if (parsed.error != null) {
            return repo to listOf(parsed.error)
        }

        val repoForCommit = if (parsed.stageAllTracked) {
            repo.copy(files = repo.files.map { file -> if (file.tracked) file.copy(staged = true) else file })
        } else {
            repo
        }

        val message = parsed.message ?: repo.commits.lastOrNull()?.message.orEmpty()
        val staged = repoForCommit.files.filter { it.staged }
        if (staged.isEmpty()) return repo to listOf("nothing to commit")

        val cleanedFiles = repoForCommit.files.map { file ->
            if (file.staged) file.copy(staged = false, tracked = true) else file
        }
        val nextCommits = if (parsed.amend && repo.commits.isNotEmpty()) {
            repo.commits.dropLast(1) + repo.commits.last().copy(message = message)
        } else {
            val nextId = "${repo.commits.size + 1}".padStart(7, '0')
            repo.commits + CommitNode(nextId, message)
        }

        return repoForCommit.copy(
            files = cleanedFiles,
            commits = nextCommits,
            branches = repo.branches + (repo.headBranch to nextCommits.size),
        ) to listOf("[${nextCommits.lastOrNull()?.id.orEmpty()}] $message")
    }

    private fun parseCommitArguments(arguments: List<String>): ParsedCommitArguments {
        var message: String? = null
        var stageAllTracked = false
        var amend = false
        var index = 0

        while (index < arguments.size) {
            val argument = arguments[index]
            when {
                argument == "-a" || argument == "--all" -> {
                    stageAllTracked = true
                }
                argument == "--amend" -> {
                    amend = true
                }
                argument == "--no-edit" -> {
                    // Keep the previous commit message when amending.
                }
                argument == "--date" -> {
                    if (arguments.getOrNull(index + 1) == null) {
                        return ParsedCommitArguments(error = "error: option '--date' requires a value")
                    }
                    index += 1
                }
                argument.startsWith("--date=") -> {
                    // The sandbox records commit structure, not timestamps.
                }
                argument == "-m" || argument == "--message" -> {
                    val next = arguments.getOrNull(index + 1)
                        ?: return ParsedCommitArguments(error = "error: commit message required. Use git commit -m \"message\"")
                    message = next
                    index += 1
                }
                argument.startsWith("--message=") -> {
                    message = argument.substringAfter('=')
                }
                argument.startsWith("-") && !argument.startsWith("--") && argument.length > 2 -> {
                    val shortFlags = argument.drop(1)
                    var shortIndex = 0
                    while (shortIndex < shortFlags.length) {
                        when (val flag = shortFlags[shortIndex]) {
                            'a' -> stageAllTracked = true
                            'm' -> {
                                val attachedValue = shortFlags.substring(shortIndex + 1)
                                if (attachedValue.isNotEmpty()) {
                                    message = attachedValue
                                } else {
                                    val next = arguments.getOrNull(index + 1)
                                        ?: return ParsedCommitArguments(error = "error: commit message required. Use git commit -m \"message\"")
                                    message = next
                                    index += 1
                                }
                                break
                            }
                            else -> return ParsedCommitArguments(error = "error: unsupported commit option '-$flag'")
                        }
                        shortIndex += 1
                    }
                }
                else -> return ParsedCommitArguments(error = "error: unsupported commit argument '$argument'")
            }
            index += 1
        }

        if (!amend && message.isNullOrBlank()) {
            return ParsedCommitArguments(error = "error: commit message required. Use git commit -m \"message\"")
        }

        return ParsedCommitArguments(message = message, stageAllTracked = stageAllTracked, amend = amend)
    }

    private fun statusLines(repo: RepoState): List<String> {
        val staged = repo.files.filter { it.staged }.map {
            when {
                it.deleted -> "deleted:    ${it.name}"
                it.tracked -> "modified:   ${it.name}"
                else -> "new file:   ${it.name}"
            }
        }
        val deleted = repo.files.filter { it.deleted && it.tracked && !it.staged }.map { "deleted:    ${it.name}" }
        val unstaged = repo.files.filterNot { it.staged || it.tracked || it.deleted }.map { "untracked:  ${it.name}" }
        return buildList {
            add("On branch ${repo.headBranch}")
            if (staged.isEmpty() && deleted.isEmpty() && unstaged.isEmpty()) {
                add("nothing to commit, working tree clean")
            } else {
                if (staged.isNotEmpty()) {
                    add("Changes to be committed:")
                    addAll(staged)
                }
                if (deleted.isNotEmpty()) {
                    add("Changes not staged for commit:")
                    addAll(deleted)
                }
                if (unstaged.isNotEmpty()) {
                    add("Untracked files:")
                    addAll(unstaged)
                }
            }
        }
    }

    private fun String.hasGlob(): Boolean = any { it == '*' || it == '?' }

    private fun String.globToRegex(): Regex {
        val pattern = buildString {
            append('^')
            this@globToRegex.forEach { char ->
                when (char) {
                    '*' -> append("[^/]*")
                    '?' -> append("[^/]")
                    '.', '(', ')', '+', '|', '^', '$', '@', '%', '{', '}', '[', ']', '\\' -> {
                        append('\\')
                        append(char)
                    }
                    else -> append(char)
                }
            }
            append('$')
        }
        return Regex(pattern)
    }

    private data class ParsedCommitArguments(
        val message: String? = null,
        val stageAllTracked: Boolean = false,
        val amend: Boolean = false,
        val error: String? = null,
    )
}