decision/frontend/app/utils/mode-params.ts

/**
 * TypeScript mirror of the Python mode_params parser.
 *
 * A mode-params string encodes voting formula parameters in a compact format.
 * Example: "D30M50B.1G.2T.1"
 *
 * Supported codes:
 *   D = duration_days (int)
 *   M = majority_pct (int, 0-100)
 *   B = base_exponent (float)
 *   G = gradient_exponent (float)
 *   C = constant_base (float)
 *   S = smith_exponent (float)
 *   T = techcomm_exponent (float)
 *   N = ratio_multiplier (float)
 *   R = is_ratio_mode (bool, 0 or 1)
 *
 * Values may start with a dot for decimals < 1, e.g. "B.1" means base_exponent=0.1.
 */

export interface ModeParams {
  duration_days: number
  majority_pct: number
  base_exponent: number
  gradient_exponent: number
  constant_base: number
  smith_exponent: number | null
  techcomm_exponent: number | null
  ratio_multiplier: number | null
  is_ratio_mode: boolean
}

type CodeType = 'int' | 'float' | 'bool'

const CODES: Record<string, { key: keyof ModeParams; type: CodeType }> = {
  D: { key: 'duration_days', type: 'int' },
  M: { key: 'majority_pct', type: 'int' },
  B: { key: 'base_exponent', type: 'float' },
  G: { key: 'gradient_exponent', type: 'float' },
  C: { key: 'constant_base', type: 'float' },
  S: { key: 'smith_exponent', type: 'float' },
  T: { key: 'techcomm_exponent', type: 'float' },
  N: { key: 'ratio_multiplier', type: 'float' },
  R: { key: 'is_ratio_mode', type: 'bool' },
}

const PARAM_RE = /([A-Z])(\d*\.?\d+)/g

function getDefaults(): ModeParams {
  return {
    duration_days: 30,
    majority_pct: 50,
    base_exponent: 0.1,
    gradient_exponent: 0.2,
    constant_base: 0.0,
    smith_exponent: null,
    techcomm_exponent: null,
    ratio_multiplier: null,
    is_ratio_mode: false,
  }
}

/**
 * Parse a mode-params string into a structured ModeParams object.
 *
 * @param paramsStr - Compact parameter string, e.g. "D30M50B.1G.2T.1"
 * @returns Parsed parameters with defaults for codes not found
 * @throws Error if an unrecognised code letter is found
 */
export function parseModeParams(paramsStr: string): ModeParams {
  const result = getDefaults()

  if (!paramsStr || !paramsStr.trim()) {
    return result
  }

  let match: RegExpExecArray | null
  PARAM_RE.lastIndex = 0

  while ((match = PARAM_RE.exec(paramsStr)) !== null) {
    const code = match[1]
    const rawValue = match[2]

    if (!(code in CODES)) {
      throw new Error(`Code de parametre inconnu : '${code}'`)
    }

    const { key, type } = CODES[code]

    if (type === 'int') {
      ;(result as any)[key] = Math.floor(parseFloat(rawValue))
    } else if (type === 'float') {
      ;(result as any)[key] = parseFloat(rawValue)
    } else if (type === 'bool') {
      ;(result as any)[key] = parseFloat(rawValue) !== 0
    }
  }

  return result
}

/**
 * Encode a ModeParams object into a compact mode-params string.
 *
 * Only includes parameters that differ from defaults.
 *
 * @param params - Parameters to encode
 * @returns Compact string, e.g. "D30M50B.1G.2"
 */
export function encodeModeParams(params: Partial<ModeParams>): string {
  const defaults = getDefaults()
  const parts: string[] = []

  const codeEntries = Object.entries(CODES) as [string, { key: keyof ModeParams; type: CodeType }][]

  for (const [code, { key, type }] of codeEntries) {
    const value = params[key]
    if (value === undefined || value === null) continue
    if (value === defaults[key]) continue

    if (type === 'int') {
      parts.push(`${code}${value}`)
    } else if (type === 'float') {
      const numVal = value as number
      if (numVal < 1 && numVal > 0) {
        parts.push(`${code}${numVal.toString().replace(/^0/, '')}`)
      } else {
        parts.push(`${code}${numVal}`)
      }
    } else if (type === 'bool') {
      parts.push(`${code}${value ? 1 : 0}`)
    }
  }

  return parts.join('')
}

/**
 * Format a mode-params string for human display.
 *
 * @param paramsStr - Compact parameter string
 * @returns Human-readable description in French
 */
export function formatModeParams(paramsStr: string): string {
  const params = parseModeParams(paramsStr)
  const parts: string[] = []

  parts.push(`Duree: ${params.duration_days} jours`)
  parts.push(`Majorite: ${params.majority_pct}%`)
  parts.push(`Base: ${params.base_exponent}`)
  parts.push(`Gradient: ${params.gradient_exponent}`)

  if (params.constant_base > 0) {
    parts.push(`Constante: ${params.constant_base}`)
  }
  if (params.smith_exponent !== null) {
    parts.push(`Smith: ${params.smith_exponent}`)
  }
  if (params.techcomm_exponent !== null) {
    parts.push(`TechComm: ${params.techcomm_exponent}`)
  }

  return parts.join(' | ')
}