# /******************************************************************
# Scale ID:          CASP-12
# Scale Name:        CASP-12 Quality of Life Scale
# TILDA Variables:   MHcasp12_control; MHcasp12_autonomy; MHcasp12_pleasure;
#                    MHcasp12_selfreal; MHcasp12_total
# Dataset:           TILDA Waves 1-7
# Author:
# Institution:       The Irish Longitudinal Study on Ageing (TILDA)
#
# Description:
# Creates the CASP-19 Quality of Life scale and all associated sub-scales.
#
# Version:           1.0
# Date:              2026-09-01
# Language:          R
#
# Assumption:
# The working data frame is called `data`.
#
# This translation preserves the Stata scoring logic as written.
# ******************************************************************/

# ********************************
# ** CASP-12 Quality of Life **
# ********************************
#
# The abbreviated CASP-12 scale replaces CASP-19
#
# Item wording and domains for CASP-12
# Questions are SCQCASP#
#
# CONTROL
# 1.  My age prevents me from doing the things I would like to
# 2.  I feel that what happens to me is out of my control
# 3.  I feel free to plan for the future
# 4.  I feel left out of things
#
# AUTONOMY
# 7.  I feel that I can please myself what I can do
# 8.  My health stops me from doing the things I want to do
# 9.  Shortage of money stops me from doing the things that I want to do
#
# PLEASURE
# 10. I look forward to each day
# 11. I feel that my life has meaning
# 13. I enjoy being in the company of others
#
# SELF-REALIZATION
# 17. I feel satisfied with the way my life has turned out
# 18. I feel that life is full of opportunities
#
# Responses are coded Often 1, Not Often 2, Sometimes 3, and Never 4.
# Items 1, 2, 4, 8 and 9 are reverse coded in the source scoring.
#
# Each subscale is calculated separately and then added together
# to provide the total score.


# Recode errors (multiple boxes ticked by R) and refusals to missing
# Equivalent to:
# mvdecode SCQCASP*, mv(-99=. \ -812=. \ -823=. \ -834=.)

casp_vars <- grep("^SCQCASP", names(data), value = TRUE)

for (var in casp_vars) {
  data[[var]][data[[var]] %in% c(-99, -812, -823, -834)] <- NA
}


# CASP-12 Control
data$MHcasp12_control <- NA_real_
data$MHcasp12_control[!is.na(data$in_scq) & data$in_scq == 1] <- 0

data$MHcasp12_control <-
  (data$SCQCASP1 - 1) +
  (data$SCQCASP2 - 1) +
  (4 - data$SCQCASP3) +
  (data$SCQCASP4 - 1)

attr(data$MHcasp12_control, "label") <- "CASP-12 Control"


# CASP-12 Autonomy
data$MHcasp12_autonomy <- NA_real_
data$MHcasp12_autonomy[!is.na(data$in_scq) & data$in_scq == 1] <- 0

data$MHcasp12_autonomy <-
  (4 - data$SCQCASP7) +
  (data$SCQCASP8 - 1) +
  (data$SCQCASP9 - 1)

attr(data$MHcasp12_autonomy, "label") <- "CASP-12 Autonomy"


# CASP-12 Pleasure
data$MHcasp12_pleasure <- NA_real_
data$MHcasp12_pleasure[!is.na(data$in_scq) & data$in_scq == 1] <- 0

data$MHcasp12_pleasure <-
  (4 - data$SCQCASP13) +
  (4 - data$SCQCASP10) +
  (4 - data$SCQCASP11)

attr(data$MHcasp12_pleasure, "label") <- "CASP-12 Pleasure"


# CASP-12 Self-Realisation
data$MHcasp12_selfreal <- NA_real_
data$MHcasp12_selfreal[!is.na(data$in_scq) & data$in_scq == 1] <- 0

data$MHcasp12_selfreal <-
  (4 - data$SCQCASP17) +
  (4 - data$SCQCASP18)

attr(data$MHcasp12_selfreal, "label") <- "CASP-12 Self-Realisation"


# CASP-12 total
data$MHcasp12_total <-
  data$MHcasp12_control +
  data$MHcasp12_autonomy +
  data$MHcasp12_pleasure +
  data$MHcasp12_selfreal

attr(data$MHcasp12_total, "label") <- "CASP-12 Quality of Life Scale"
attr(data$MHcasp12_total, "note")  <- "CASP is a 12-item scale"