import { SectionConfig, BuiltinFormat } from '../types';
import { toMarkdownTable } from '../viz/table-renderer';

// ---------------------------------------------------------------------------
// Section → Markdown
// ---------------------------------------------------------------------------

export function formatSection(rows: Record<string, unknown>[], section: SectionConfig): string {
  if (rows.length === 0) return `### ${section.heading}\n\n*No data.*\n`;

  const heading = `### ${section.heading}\n\n`;

  if (section.format.type === 'custom' && section.format.customTemplate) {
    return heading + applyCustomTemplate(rows, section.format.customTemplate) + '\n';
  }

  const fmt = section.format.builtin;
  if (!fmt) return heading + formatAsTable(rows) + '\n';

  switch (fmt.name) {
    case 'timeline':
      return heading + formatAsTimeline(rows, fmt.showTimestamp, fmt.showPayload) + '\n';
    case 'table':
      return heading + formatAsTableWithColumns(rows, fmt.columns) + '\n';
    case 'summary':
      return heading + formatAsSummary(rows, fmt.metrics) + '\n';
    case 'metric':
      return heading + formatAsMetric(rows, fmt) + '\n';
    case 'heatmap':
      return heading + formatAsHeatmap(rows, fmt.labelField, fmt.valueField) + '\n';
    default:
      return heading + formatAsTable(rows) + '\n';
  }
}

// ---------------------------------------------------------------------------
// Timeline
// ---------------------------------------------------------------------------

function formatAsTimeline(rows: Record<string, unknown>[], showTs: boolean, showPayload: boolean): string {
  const lines: string[] = [];
  for (const row of rows) {
    const parts: string[] = [];
    if (showTs && row.timestamp != null) {
      const ts = typeof row.timestamp === 'number'
        ? new Date(row.timestamp).toLocaleTimeString()
        : String(row.timestamp);
      parts.push(`**${ts}**`);
    }
    parts.push(String(row.type ?? ''));
    if (row.source) parts.push(`\`${row.source}\``);
    if (showPayload && row.payload) {
      const p = typeof row.payload === 'string' ? row.payload : JSON.stringify(row.payload);
      if (p !== '{}') parts.push(`— ${p}`);
    }
    lines.push(`- ${parts.join(' ')}`);
  }
  return lines.join('\n');
}

// ---------------------------------------------------------------------------
// Table
// ---------------------------------------------------------------------------

function formatAsTable(rows: Record<string, unknown>[]): string {
  const keys = Object.keys(rows[0]);
  return toMarkdownTable(keys, rows);
}

function formatAsTableWithColumns(
  rows: Record<string, unknown>[],
  columns: { header: string; value: string; align?: string }[],
): string {
  const headers = columns.map(c => c.header);
  const mappedRows = rows.map(row => {
    const mapped: Record<string, unknown> = {};
    for (const col of columns) {
      mapped[col.header] = row[col.value] ?? '';
    }
    return mapped;
  });
  return toMarkdownTable(headers, mappedRows);
}

// ---------------------------------------------------------------------------
// Summary
// ---------------------------------------------------------------------------

function formatAsSummary(
  rows: Record<string, unknown>[],
  metrics: { label: string; aggregate: string; field?: string }[],
): string {
  const lines: string[] = [];
  for (const m of metrics) {
    const values = rows.map(r => Number(r[m.field ?? 'count'] ?? 0));
    let result: number;
    switch (m.aggregate) {
      case 'sum': result = values.reduce((a, b) => a + b, 0); break;
      case 'avg': result = values.length > 0 ? values.reduce((a, b) => a + b, 0) / values.length : 0; break;
      case 'min': result = values.length > 0 ? Math.min(...values) : 0; break;
      case 'max': result = values.length > 0 ? Math.max(...values) : 0; break;
      default: result = rows.length;
    }
    lines.push(`- **${m.label}**: ${result.toLocaleString()}`);
  }
  return lines.join('\n');
}

// ---------------------------------------------------------------------------
// Metric
// ---------------------------------------------------------------------------

function formatAsMetric(
  rows: Record<string, unknown>[],
  fmt: { aggregate: string; field?: string },
): string {
  const values = rows.map(r => Number(r[fmt.field ?? Object.keys(r).pop()!] ?? 0));
  let result: number;
  switch (fmt.aggregate) {
    case 'sum': result = values.reduce((a, b) => a + b, 0); break;
    case 'avg': result = values.length > 0 ? values.reduce((a, b) => a + b, 0) / values.length : 0; break;
    case 'min': result = values.length > 0 ? Math.min(...values) : 0; break;
    case 'max': result = values.length > 0 ? Math.max(...values) : 0; break;
    default: result = rows.length;
  }
  return `**${result.toLocaleString()}**`;
}

// ---------------------------------------------------------------------------
// Heatmap
// ---------------------------------------------------------------------------

function formatAsHeatmap(rows: Record<string, unknown>[], labelField: string, valueField: string): string {
  const maxVal = Math.max(...rows.map(r => Number(r[valueField] ?? 0)), 1);
  const lines: string[] = [];
  for (const row of rows) {
    const label = String(row[labelField] ?? '');
    const val = Number(row[valueField] ?? 0);
    const barLen = Math.round((val / maxVal) * 30);
    const bar = '\u2588'.repeat(barLen);
    lines.push(`\`${label.padEnd(12)}\` ${bar} ${val}`);
  }
  return lines.join('\n');
}

// ---------------------------------------------------------------------------
// Custom template
// ---------------------------------------------------------------------------

function applyCustomTemplate(rows: Record<string, unknown>[], template: string): string {
  return template.replace(/\{\{rows\}\}/g, JSON.stringify(rows, null, 2));
}

// ---------------------------------------------------------------------------
// Frontmatter
// ---------------------------------------------------------------------------

export function buildFrontmatter(data: Record<string, string>): string {
  if (Object.keys(data).length === 0) return '';
  const lines = ['---'];
  for (const [key, value] of Object.entries(data)) {
    lines.push(`${key}: ${value}`);
  }
  lines.push('---', '');
  return lines.join('\n');
}

// ---------------------------------------------------------------------------
// Date placeholders
// ---------------------------------------------------------------------------

export function resolvePlaceholders(pattern: string, context: { date?: Date; sessionId?: string }): string {
  const d = context.date ?? new Date();
  return pattern
    .replace(/\{\{date\}\}/g, d.toISOString().substring(0, 10))
    .replace(/\{\{year\}\}/g, String(d.getFullYear()))
    .replace(/\{\{month\}\}/g, String(d.getMonth() + 1).padStart(2, '0'))
    .replace(/\{\{day\}\}/g, String(d.getDate()).padStart(2, '0'))
    .replace(/\{\{sessionId\}\}/g, context.sessionId ?? '');
}