package soy.iko.opencode.ui.components

import androidx.compose.foundation.background
import androidx.compose.foundation.horizontalScroll
import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxWidth
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.width
import androidx.compose.foundation.rememberScrollState
import androidx.compose.foundation.shape.RoundedCornerShape
import androidx.compose.foundation.verticalScroll
import androidx.compose.material.icons.Icons
import androidx.compose.material.icons.filled.ContentCopy
import androidx.compose.material3.Icon
import androidx.compose.material3.IconButton
import androidx.compose.material3.MaterialTheme
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.clip
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.unit.dp

/** A single line of a parsed unified diff. */
sealed interface DiffLine {
    val text: String

    data class Hunk(override val text: String) : DiffLine          // @@ ... @@
    data class FileHeader(override val text: String) : DiffLine    // --- / +++
    data class Context(override val text: String) : DiffLine
    data class Add(override val text: String) : DiffLine
    data class Remove(override val text: String) : DiffLine
}

/** Parse a unified diff string into typed [DiffLine]s. */
fun parseDiff(diff: String): List<DiffLine> {
    val result = mutableListOf<DiffLine>()
    for (raw in diff.split("\n")) {
        when {
            raw.startsWith("@@") -> result.add(DiffLine.Hunk(raw))
            raw.startsWith("---") || raw.startsWith("+++") -> result.add(DiffLine.FileHeader(raw))
            raw.startsWith("+") -> result.add(DiffLine.Add(raw.removePrefix("+")))
            raw.startsWith("-") -> result.add(DiffLine.Remove(raw.removePrefix("-")))
            raw.startsWith(" ") -> result.add(DiffLine.Context(raw.removePrefix(" ")))
            raw.startsWith("diff ") || raw.startsWith("index ") -> result.add(DiffLine.FileHeader(raw))
            raw.isNotBlank() -> result.add(DiffLine.Context(raw))
        }
    }
    return result
}

/** Heuristic: does this string look like a unified diff? */
fun looksLikeDiff(text: String): Boolean {
    val lines = text.lineSequence()
    var hunkCount = 0
    var addCount = 0
    var removeCount = 0
    for (line in lines) {
        when {
            line.startsWith("@@") -> hunkCount++
            line.startsWith("+") && !line.startsWith("+++") -> addCount++
            line.startsWith("-") && !line.startsWith("---") -> removeCount++
        }
        if (hunkCount >= 1 && (addCount + removeCount) >= 1) return true
    }
    return false
}

@Composable
fun DiffView(diff: String, modifier: Modifier = Modifier) {
    val lines = remember(diff) { parseDiff(diff) }
    val addColor = MaterialTheme.colorScheme.primary.copy(alpha = 0.15f)
    val removeColor = MaterialTheme.colorScheme.error.copy(alpha = 0.15f)
    val addText = MaterialTheme.colorScheme.primary
    val removeText = MaterialTheme.colorScheme.error
    val context = LocalContext.current

    Column(
        modifier = modifier
            .fillMaxWidth()
            .padding(vertical = 4.dp)
            .clip(RoundedCornerShape(8.dp))
            .background(MaterialTheme.colorScheme.surfaceVariant)
            .padding(top = 2.dp, end = 4.dp),
    ) {
        Row(modifier = Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.End) {
            IconButton(onClick = { copyToClipboard(context, "diff", diff) }) {
                Icon(Icons.Filled.ContentCopy, contentDescription = "Copy", tint = MaterialTheme.colorScheme.onSurfaceVariant)
            }
        }
        Column(
            modifier = Modifier
                .horizontalScroll(rememberScrollState())
                .verticalScroll(rememberScrollState())
                .padding(horizontal = 10.dp)
                .padding(bottom = 10.dp),
        ) {
            for (line in lines) {
                when (line) {
                    is DiffLine.Hunk -> Text(
                        line.text,
                        style = MaterialTheme.typography.bodySmall,
                        fontFamily = FontFamily.Monospace,
                        color = MaterialTheme.colorScheme.tertiary,
                        modifier = Modifier.padding(vertical = 2.dp),
                    )
                    is DiffLine.FileHeader -> Text(
                        line.text,
                        style = MaterialTheme.typography.bodySmall,
                        fontFamily = FontFamily.Monospace,
                        color = MaterialTheme.colorScheme.onSurfaceVariant,
                        modifier = Modifier.padding(vertical = 1.dp),
                    )
                    is DiffLine.Add -> DiffRow(line.text, "+", addColor, addText)
                    is DiffLine.Remove -> DiffRow(line.text, "-", removeColor, removeText)
                    is DiffLine.Context -> DiffRow(line.text, " ", Color.Transparent, MaterialTheme.colorScheme.onSurface)
                }
            }
        }
    }
}

@Composable
private fun DiffRow(text: String, prefix: String, bg: Color, textColor: androidx.compose.ui.graphics.Color) {
    Row(
        modifier = Modifier.fillMaxWidth().background(bg),
    ) {
        Text(
            prefix,
            style = MaterialTheme.typography.bodySmall,
            fontFamily = FontFamily.Monospace,
            color = textColor,
            modifier = Modifier.width(16.dp),
        )
        Text(
            text,
            style = MaterialTheme.typography.bodySmall,
            fontFamily = FontFamily.Monospace,
            color = textColor,
        )
    }
}