import mjml2html from 'mjml'

function getPath(data, path) {
  return String(path || '').split('.').filter(Boolean).reduce((value, key) => value?.[key], data)
}

export function escapeHtml(value) {
  return String(value ?? '')
    .replaceAll('&', '&')
    .replaceAll('<', '&lt;')
    .replaceAll('>', '&gt;')
    .replaceAll('"', '&quot;')
    .replaceAll("'", '&#039;')
}

export function interpolate(input, data) {
  return String(input ?? '').replace(/{{\s*([\w.[\]-]+)\s*}}/g, (_, path) => {
    const normalized = path.replace(/\[(\d+)\]/g, '.$1')
    const value = getPath(data, normalized)
    return value == null ? '' : String(value)
  })
}

function safeUrl(input, data) {
  const url = interpolate(input, data).trim()
  return /^(https?:|mailto:)/i.test(url) ? url : '#'
}

function safeHex(value, fallback) {
  const color = String(value || '').trim()
  return /^#[0-9a-f]{3}([0-9a-f]{3})?$/i.test(color) ? color : fallback
}

function safeNumber(value, fallback, min, max) {
  const number = Number(value)
  if (!Number.isFinite(number)) return fallback
  return Math.min(max, Math.max(min, number))
}

function safeAlign(value) {
  return ['left', 'center', 'right'].includes(value) ? value : 'left'
}

function safeFont(value) {
  const font = String(value || '')
  const allowed = ['Arial', 'Helvetica', 'Verdana', 'Georgia', 'Times New Roman', 'system-ui']
  return allowed.includes(font) ? font : 'Arial'
}

function themeOf(template) {
  const theme = template?.theme || {}
  return {
    backgroundColor: safeHex(theme.backgroundColor, '#f8fafc'),
    surfaceColor: safeHex(theme.surfaceColor, '#ffffff'),
    textColor: safeHex(theme.textColor, '#172033'),
    mutedColor: safeHex(theme.mutedColor, '#64748b'),
    accentColor: safeHex(theme.accentColor, '#111827'),
    buttonTextColor: safeHex(theme.buttonTextColor, '#ffffff'),
    borderColor: safeHex(theme.borderColor, '#dbe2ea'),
    borderRadius: safeNumber(theme.borderRadius, 12, 0, 32),
    pagePadding: safeNumber(theme.pagePadding, 18, 0, 40),
    fontFamily: safeFont(theme.fontFamily),
    pageBackgroundImage: safeUrl(theme.pageBackgroundImage, {}),
    borderImage: safeUrl(theme.borderImage, {})
  }
}

function reportBlockStyle(block, theme) {
  const style = block?.style || {}
  const rules = [
    `background:${safeHex(style.backgroundColor, 'transparent')}`,
    `color:${safeHex(style.textColor, theme.textColor)}`,
    `border-color:${safeHex(style.borderColor, theme.borderColor)}`,
    `border-width:${safeNumber(style.borderWidth, 0, 0, 8)}px`,
    'border-style:solid',
    `border-radius:${safeNumber(style.borderRadius, theme.borderRadius, 0, 32)}px`,
    `padding:${safeNumber(style.padding, 0, 0, 48)}px`,
    `text-align:${safeAlign(style.align)}`
  ]
  return rules.join(';')
}

function wrapReportBlock(block, theme, html) {
  return `<div class="block" style="${reportBlockStyle(block, theme)}">${html}</div>`
}

function renderTable(block, data) {
  const rows = getPath(data, block.props?.rowsPath) || []
  const columns = Array.isArray(block.props?.columns) ? block.props.columns : []
  if (!Array.isArray(rows)) return ''
  return `<div class="table-wrap"><table><thead><tr>${columns.map(c => `<th>${escapeHtml(c.label)}</th>`).join('')}</tr></thead><tbody>${rows.map(row => `<tr>${columns.map(c => `<td>${escapeHtml(getPath(row, c.key))}</td>`).join('')}</tr>`).join('')}</tbody></table></div>`
}

function blockHtml(block, data, theme) {
  const p = block.props || {}
  let html = ''
  switch (block.type) {
    case 'heading':
      html = `<h2>${escapeHtml(interpolate(p.text, data))}</h2>`
      break
    case 'text':
      html = `<p>${escapeHtml(interpolate(p.text, data))}</p>`
      break
    case 'kpi':
      html = `<div class="kpi"><span>${escapeHtml(interpolate(p.label, data))}</span><strong>${escapeHtml(interpolate(p.value, data))}</strong></div>`
      break
    case 'button':
      html = `<p><a class="button" href="${escapeHtml(safeUrl(p.url, data))}">${escapeHtml(interpolate(p.text, data))}</a></p>`
      break
    case 'image':
      html = `<img class="image" src="${escapeHtml(safeUrl(p.url, data))}" alt="${escapeHtml(interpolate(p.alt, data))}" />`
      break
    case 'divider':
      html = '<hr />'
      break
    case 'table':
      html = renderTable(block, data)
      break
    default:
      return ''
  }
  return wrapReportBlock(block, theme, html)
}

export function renderReportHtml(template, data = {}) {
  const blocks = template?.blocks || []
  const theme = themeOf(template)
  const backgroundImage = theme.pageBackgroundImage === '#' ? 'none' : `url("${escapeHtml(theme.pageBackgroundImage)}")`
  const borderImage = theme.borderImage === '#' ? 'none' : `url("${escapeHtml(theme.borderImage)}") 30 stretch`

  return `<!doctype html>
<html><head><meta charset="utf-8"><meta name="viewport" content="width=device-width,initial-scale=1">
<style>
@page{size:A4;margin:14mm}*{box-sizing:border-box}body{font:${15}px/1.5 ${theme.fontFamily},sans-serif;color:${theme.textColor};margin:0;background:${theme.backgroundColor};background-image:${backgroundImage};background-size:cover;background-position:center;background-repeat:no-repeat}.document{min-height:100%;background:${theme.surfaceColor};padding:${theme.pagePadding}px;border:${theme.borderImage === '#' ? 0 : 12}px solid transparent;border-image:${borderImage};border-radius:${theme.borderRadius}px}.block{margin:0 0 12px}.block:last-child{margin-bottom:0}h2{font-size:24px;margin:0 0 16px;color:inherit}p{margin:0 0 14px}.kpi{border:1px solid ${theme.borderColor};border-radius:${theme.borderRadius}px;padding:14px;display:flex;justify-content:space-between;gap:16px;background:${theme.surfaceColor}}.kpi span{color:${theme.mutedColor}}.kpi strong{font-size:18px}.button{display:inline-block;background:${theme.accentColor};color:${theme.buttonTextColor};text-decoration:none;padding:10px 16px;border-radius:${theme.borderRadius}px}.image{max-width:100%;height:auto;border-radius:${theme.borderRadius}px}hr{border:0;border-top:1px solid ${theme.borderColor};margin:18px 0}.table-wrap{overflow:hidden;border:1px solid ${theme.borderColor};border-radius:${theme.borderRadius}px}table{border-collapse:collapse;width:100%;font-size:13px}th,td{padding:9px 10px;text-align:left;border-bottom:1px solid ${theme.borderColor}}th{background:${theme.backgroundColor}}
</style></head><body><main class="document">${blocks.map(block => blockHtml(block, data, theme)).join('\n')}</main></body></html>`
}

function emailBlock(block, data, theme) {
  const p = block.props || {}
  const style = block.style || {}
  const padding = `${safeNumber(style.padding, 0, 0, 48)}px`
  const align = safeAlign(style.align)
  const color = safeHex(style.textColor, theme.textColor)
  const backgroundColor = safeHex(style.backgroundColor, theme.surfaceColor)
  const borderColor = safeHex(style.borderColor, theme.borderColor)
  const borderWidth = safeNumber(style.borderWidth, 0, 0, 8)
  const radius = safeNumber(style.borderRadius, theme.borderRadius, 0, 32)
  const common = `padding="${padding}" align="${align}" color="${color}"`

  switch (block.type) {
    case 'heading':
      return `<mj-text ${common} font-size="24px" font-weight="700" container-background-color="${backgroundColor}">${escapeHtml(interpolate(p.text, data))}</mj-text>`
    case 'text':
      return `<mj-text ${common} container-background-color="${backgroundColor}">${escapeHtml(interpolate(p.text, data))}</mj-text>`
    case 'kpi':
      return `<mj-text padding="${padding}" color="${theme.mutedColor}" container-background-color="${backgroundColor}">${escapeHtml(interpolate(p.label, data))}</mj-text><mj-text padding="0 ${padding} ${padding}" color="${color}" font-size="22px" font-weight="700" container-background-color="${backgroundColor}">${escapeHtml(interpolate(p.value, data))}</mj-text>`
    case 'button':
      return `<mj-button background-color="${safeHex(style.backgroundColor, theme.accentColor)}" color="${safeHex(style.textColor, theme.buttonTextColor)}" border-radius="${radius}px" href="${escapeHtml(safeUrl(p.url, data))}">${escapeHtml(interpolate(p.text, data))}</mj-button>`
    case 'image':
      return `<mj-image padding="${padding}" border="${borderWidth}px solid ${borderColor}" border-radius="${radius}px" src="${escapeHtml(safeUrl(p.url, data))}" alt="${escapeHtml(interpolate(p.alt, data))}" />`
    case 'divider':
      return `<mj-divider border-color="${borderColor}" border-width="${Math.max(1, borderWidth)}px" />`
    default:
      return '<mj-text color="#64748b">This block is available in report output only.</mj-text>'
  }
}

export function renderEmailHtml(template, data = {}) {
  const theme = themeOf(template)
  const body = (template?.blocks || []).map(block => emailBlock(block, data, theme)).join('\n')
  const backgroundUrl = theme.pageBackgroundImage === '#' ? '' : ` background-url="${escapeHtml(theme.pageBackgroundImage)}" background-size="cover" background-repeat="no-repeat"`
  const mjml = `<mjml><mj-head><mj-attributes><mj-all font-family="${theme.fontFamily}, sans-serif" /><mj-text font-size="15px" line-height="1.5" color="${theme.textColor}" /></mj-attributes></mj-head><mj-body background-color="${theme.backgroundColor}"><mj-section background-color="${theme.surfaceColor}" padding="${theme.pagePadding}px"${backgroundUrl}><mj-column>${body}</mj-column></mj-section></mj-body></mjml>`
  const result = mjml2html(mjml, { validationLevel: 'soft' })
  if (result.errors?.length) console.warn('MJML warnings', result.errors)
  return result.html
}