# CREATE_MAX_MOSAIC.R
# ===================
# Create maximum value mosaics (Chlorophyll Index) for current and previous weeks
# Uses pre-processed merged_final_tif files (already have 5 bands)
# Usage: Rscript create_max_mosaic.R [end_date] [project_dir]
# Example: Rscript r_app/create_max_mosaic.R 2025-12-24 angata

library(terra)
library(here)
library(lubridate)

main <- function() {
  args <- commandArgs(trailingOnly = TRUE)
  
  # Parse arguments
  end_date <- if (length(args) >= 1 && !is.na(args[1])) {
    as.Date(args[1])
  } else {
    Sys.Date()
  }
  
  project_dir <- if (length(args) >= 2) args[2] else "angata"
  
  cat(sprintf("Creating MAX mosaics (Chlorophyll Index): end_date=%s, project=%s\n", 
              format(end_date, "%Y-%m-%d"), project_dir))
  
  # Calculate date ranges
  current_week_start <- end_date - 6  # Last 7 days
  prev_week_start <- end_date - 13     # 7-14 days back
  prev_week_end <- end_date - 7
  
  cat(sprintf("Current week: %s to %s\n", format(current_week_start, "%Y-%m-%d"), format(end_date, "%Y-%m-%d")))
  cat(sprintf("Previous week: %s to %s\n", format(prev_week_start, "%Y-%m-%d"), format(prev_week_end, "%Y-%m-%d")))
  
  # Set up paths
  tif_dir <- here("laravel_app/storage/app", project_dir, "merged_final_tif")
  output_dir <- here("laravel_app/storage/app", project_dir, "weekly_mosaic")
  dir.create(output_dir, showWarnings = FALSE, recursive = TRUE)
  
  # Find all TIF files
  tif_files <- list.files(tif_dir, pattern = "\\.tif$", full.names = TRUE)
  
  if (length(tif_files) == 0) {
    cat("✗ No TIF files found in:", tif_dir, "\n")
    return(FALSE)
  }
  
  cat(sprintf("✓ Found %d total TIF files\n", length(tif_files)))
  
  # Extract dates from filenames (assumes YYYY-MM-DD.tif format)
  extract_date_from_filename <- function(filepath) {
    basename <- basename(filepath)
    # Extract date part before .tif
    date_str <- sub("\\.tif$", "", basename)
    tryCatch(as.Date(date_str), error = function(e) NA)
  }
  
  # Filter files by date range
  filter_files_by_date <- function(files, start_date, end_date) {
    dates <- sapply(files, extract_date_from_filename)
    valid_idx <- !is.na(dates) & dates >= start_date & dates <= end_date
    files[valid_idx]
  }
  
  # Create mosaic for date range
  create_mosaic <- function(files, output_path, week_label) {
    if (length(files) == 0) {
      cat(sprintf("⚠ No files found for %s\n", week_label))
      return(FALSE)
    }
    
    cat(sprintf("\n%s: Processing %d files\n", week_label, length(files)))
    
    # Read all TIFs
    cat("  Reading TIFs...\n")
    rast_list <- lapply(files, function(f) {
      tryCatch(rast(f), error = function(e) {
        cat(sprintf("  ⚠ Failed to read: %s\n", basename(f)))
        NULL
      })
    })
    
    rast_list <- rast_list[!sapply(rast_list, is.null)]
    
    if (length(rast_list) == 0) {
      cat(sprintf("  ✗ Could not read any TIF files\n"))
      return(FALSE)
    }
    
    cat(sprintf("  ✓ Successfully read %d TIFs\n", length(rast_list)))
    
    # Stack them
    cat("  Stacking rasters...\n")
    stacked <- do.call(c, rast_list)
    
    # Create max mosaic (pixel-wise maximum across all dates)
    cat("  Computing maximum mosaic...\n")
    max_mosaic <- max(stacked, na.rm = TRUE)
    
    # Save
    cat(sprintf("  Saving to: %s\n", basename(output_path)))
    writeRaster(max_mosaic, output_path, overwrite = TRUE)
    cat(sprintf("  ✓ MAX mosaic created\n"))
    return(TRUE)
  }
  
  # Create both mosaics
  current_files <- filter_files_by_date(tif_files, current_week_start, end_date)
  prev_files <- filter_files_by_date(tif_files, prev_week_start, prev_week_end)
  
  success <- TRUE
  success <- create_mosaic(current_files, 
                          file.path(output_dir, "max_mosaic_current_week.tif"),
                          "CURRENT WEEK") && success
  
  success <- create_mosaic(prev_files,
                          file.path(output_dir, "max_mosaic_previous_week.tif"),
                          "PREVIOUS WEEK") && success
  
  if (success) {
    cat("\n✓ Both mosaics created successfully\n")
  }
  return(success)
}

if (sys.nframe() == 0) {
  main()
}