// Package psalter bridges psalm versification between the Vulgate-family
// versions and the Douay-Rheims source. See the Go port of psalm_versify.py.
package psalter

// DRBTitleFold maps a Hebrew psalm number to the number of title verses the DRB
// source folds into verse 1 (1, or 2 for a historical superscription). Untitled
// psalms are absent (k = 0). Copy every entry from psalm_versify.py DRB_TITLE_FOLD.
var DRBTitleFold = map[int]int{
	3: 1, 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 11: 1, 12: 1, 14: 1, 18: 1, 19: 1,
	20: 1, 21: 1, 22: 1, 30: 1, 31: 1, 34: 1, 36: 1, 38: 1, 39: 1, 40: 1,
	41: 1, 42: 1, 44: 1, 45: 1, 46: 1, 47: 1, 48: 1, 49: 1, 51: 2, 52: 2,
	53: 1, 54: 2, 55: 1, 56: 1, 57: 1, 58: 1, 59: 1, 60: 2, 61: 1, 62: 1,
	63: 1, 64: 1, 65: 1, 67: 1, 68: 1, 69: 1, 70: 1, 75: 1, 76: 1, 77: 1,
	80: 1, 81: 1, 83: 1, 84: 1, 85: 1, 88: 1, 89: 1, 92: 1, 102: 1, 108: 1,
	140: 1, 142: 1,
}

// DrbVerse returns the DRB-source verse number for a lectionary (BT) psalm verse.
func DrbVerse(hebrewPsalm, lectionaryVerse int) int {
	v := lectionaryVerse - DRBTitleFold[hebrewPsalm]
	if v < 1 {
		return 1
	}
	return v
}

// HebrewToVulgateChapter maps a Masoretic psalm number to its Vulgate chapter.
// For the split psalms (116, 147) it returns the chapter of the FIRST verse;
// use HebrewToVulgate for the verse-accurate mapping.
func HebrewToVulgateChapter(h int) int {
	c, _ := HebrewToVulgate(h, 1)
	return c
}

// HebrewToVulgate maps a Masoretic (modern) psalm number and verse to the
// Vulgate chapter and verse. Most psalms differ only by a one-off chapter shift
// with the verse unchanged, but four spans are joined or split, so the verse
// carries an offset there:
//
//	Hebrew 9  = Vulgate 9:1-21     Hebrew 10 = Vulgate 9:22-39   (10:v -> 9:v+21)
//	Hebrew 114 = Vulgate 113:1-8   Hebrew 115 = Vulgate 113:9-26 (115:v -> 113:v+8)
//	Hebrew 116:1-9  = Vulgate 114  Hebrew 116:10-19 = Vulgate 115:1-10 (116:v>=10 -> 115:v-9)
//	Hebrew 147:1-11 = Vulgate 146  Hebrew 147:12-20 = Vulgate 147:1-9  (147:v>=12 -> 147:v-11)
func HebrewToVulgate(h, v int) (chapter, verse int) {
	switch {
	case h <= 8 || h >= 148:
		return h, v
	case h == 9:
		return 9, v
	case h == 10:
		return 9, v + 21
	case h >= 11 && h <= 113:
		return h - 1, v
	case h == 114:
		return 113, v
	case h == 115:
		return 113, v + 8
	case h == 116:
		if v <= 9 {
			return 114, v
		}
		return 115, v - 9
	case h >= 117 && h <= 146:
		return h - 1, v
	case h == 147:
		if v <= 11 {
			return 146, v
		}
		return 147, v - 11
	}
	return h, v
}