package com.peachpasswords.codex

import android.graphics.Bitmap
import android.graphics.Color
import android.graphics.Paint
import android.graphics.Rect
import android.graphics.pdf.PdfDocument
import java.io.ByteArrayOutputStream

/**
 * Renders the Aztec codes onto an A4 PDF in a 6×6 grid — the printed Codex.
 * A4 at 72pt/in is 595×842pt. Header carries the verify code; the footer
 * carries the generation date and page counter so a re-collated stack stays
 * unambiguous.
 */
object CodexPdf {
    private const val PAGE_W = 595
    private const val PAGE_H = 842
    private const val MARGIN = 36f
    private const val HEADER_H = 54f
    private const val FOOTER_H = 28f

    fun render(aztecs: List<Bitmap>, manifest: CodexManifest): ByteArray {
        val doc = PdfDocument()
        val gridTop = MARGIN + HEADER_H
        val gridW = PAGE_W - 2 * MARGIN
        val gridH = PAGE_H - gridTop - MARGIN - FOOTER_H
        val cellW = gridW / CODES_PER_ROW
        val cellH = gridH / CODES_PER_COL
        val cell = minOf(cellW, cellH)
        // Tighter padding → larger codes (~78pt, close to the browser's 80pt),
        // which keeps modules above the camera/scan decode threshold.
        val pad = cell * 0.05f

        val title = Paint().apply { color = Color.BLACK; textSize = 16f; isAntiAlias = true; isFakeBoldText = true }
        val mono = Paint().apply { color = Color.rgb(0x55, 0x55, 0x55); textSize = 9f; isAntiAlias = true }
        val codePaint = Paint().apply { isFilterBitmap = false }

        val pageCount = Math.ceil(aztecs.size.toDouble() / CODES_PER_PAGE).toInt().coerceAtLeast(1)
        for (page in 0 until pageCount) {
            val info = PdfDocument.PageInfo.Builder(PAGE_W, PAGE_H, page + 1).create()
            val pg = doc.startPage(info)
            val canvas = pg.canvas

            canvas.drawText("Peach Codex", MARGIN, MARGIN + 18f, title)
            canvas.drawText(manifest.verifyCode, MARGIN, MARGIN + 36f, mono)
            canvas.drawText(
                "${manifest.entryCount} entries · ${manifest.totalChunks} codes · keep with your recovery words",
                MARGIN + 120f, MARGIN + 36f, mono,
            )

            val first = page * CODES_PER_PAGE
            val last = minOf(first + CODES_PER_PAGE, aztecs.size)
            for (idx in first until last) {
                val slot = idx - first
                val row = slot / CODES_PER_ROW
                val col = slot % CODES_PER_ROW
                val left = MARGIN + col * cell + pad
                val top = gridTop + row * cell + pad
                val dst = Rect(left.toInt(), top.toInt(), (left + cell - 2 * pad).toInt(), (top + cell - 2 * pad).toInt())
                canvas.drawBitmap(aztecs[idx], null, dst, codePaint)
            }

            canvas.drawText(
                "page ${page + 1} of $pageCount · ${manifest.verifyCode}",
                MARGIN, PAGE_H - MARGIN + 4f, mono,
            )
            doc.finishPage(pg)
        }

        val out = ByteArrayOutputStream()
        doc.writeTo(out)
        doc.close()
        return out.toByteArray()
    }
}