package parser

import (
	"fmt"
	"strconv"
	"strings"
	"time"
)

// ParseDSL parses the whitespace-structured DSL and returns a slice of Workouts and a slice of Measurements.
func ParseDSL(input string) ([]Workout, []Measurement, error) {
	lines := strings.Split(input, "\n")
	var workouts []Workout
	var measurements []Measurement
	var curWorkout *Workout
	var curSetGroup *SetGroup

	for idx, rawLine := range lines {
		line := strings.TrimRight(rawLine, "\r\n")
		if line == "" {
			continue
		}

		indent := countIndent(line)
		content := strings.TrimLeft(line, " \t")
		var setIndex int

		switch indent {
		case 0:
			// either a workout or a measurement
			parts := strings.SplitN(line, " ", 3)
			if (parts[1] == "measurement") {
			// Measurement line: date measurement Variable=Value [note]
				date, variable, value, note, err := parseMeasurementLine(content)
				if err != nil {
					return nil, nil, fmt.Errorf("line %d: %v", idx+1, err)
				}
				measurements = append(measurements, Measurement{
					Date:     date,
					Variable: variable,
					Value:    value,
					Note:     note,
				})
			} else if (parts[1] == "workout") {
				// Workout line: date workout [type in (parentheses)] [note]
				date, typ, note, err := parseWorkoutLine(content)
				if err != nil {
					return nil, nil, fmt.Errorf("line %d: %v", idx+1, err)
				}
				workouts = append(workouts, Workout{
					Date:      date,
					Type:      typ,
					Note:      note,
				SetGroups: nil,
				})
				curWorkout = &workouts[len(workouts)-1]
				curSetGroup = nil
			} else {
				return nil, nil, fmt.Errorf("Invalid top level item: %s.\n",parts[1])
			}
		case 1:
			// SetGroup line (including planned sets)
			if curWorkout == nil {
				return nil, nil, fmt.Errorf("line %d: SetGroup without Workout", idx+1)
			}
			sg, err := parseSetGroupLine(content)
			if err != nil {
				return nil, nil, fmt.Errorf("line %d: %v", idx+1, err)
			}
			curWorkout.SetGroups = append(curWorkout.SetGroups, sg)
			curSetGroup = &curWorkout.SetGroups[len(curWorkout.SetGroups)-1]
			setIndex = 0
		case 2:
			// Actual Set line (may be multiple sets separated by "-")
			if curSetGroup == nil {
				return nil, nil, fmt.Errorf("line %d: Actual Set without SetGroup", idx+1)
			}
			sets, weights, err := parseActualSetLine(content,curWorkout.Date)
			if err != nil {
				return nil, nil, fmt.Errorf("line %d: %v", idx+1, err)
			}
			for i := range(sets) {
				if !weights[i] {
					sets[i].Weight = curSetGroup.PlannedSets[setIndex].Weight
				}
				if setIndex < len(curSetGroup.PlannedSets) -1 {
					setIndex++
				}
			}
			curSetGroup.ActualSets = append(curSetGroup.ActualSets, sets...)
		default:
			return nil, nil, fmt.Errorf("line %d: Unexpected indentation", idx+1)
		}
	}

	return workouts, measurements, nil
}

// countIndent returns the number of leading whitespace "levels" (spaces or tabs).
// 0 = Workout, 1 = SetGroup, 2 = ActualSet.
func countIndent(line string) int {
	indent := 0
	for _, ch := range line {
		if ch == ' ' || ch == '\t' {
			indent++
		} else {
			break
		}
	}
	return indent
}

// parseMeasurementLine splits the Measurement line into the date, variable,
// value, and note fields.
func parseMeasurementLine(line string) (time.Time, string, float64, string, error) {
	parts := strings.SplitN(line, " ", 3)
	dateStr := parts[0]
	date, err := time.Parse("2006-01-02", dateStr)
	if err != nil {
		return time.Time{}, "", 0, "", fmt.Errorf("invalid date: %v", err)
	}
	parts = strings.SplitN(parts[2],"=",2)
	variable := parts[0]
	value, _, err := parseWeightAndUnit(parts[1])
	if err != nil {
		return time.Time{}, "", 0, "", fmt.Errorf("Cannot parse measurement value.\n")
	}
	note := ""
	if len(parts) > 2 {
		note = parts[3]
	}
	return date, variable, value, note, nil

}

// parseWorkoutLine splits the Workout line into date, type, note.
// Date is the first non-whitespace field, type is in balanced parentheses, note is the rest.
func parseWorkoutLine(line string) (time.Time, string, string, error) {
	parts := strings.SplitN(line, " ", 3)
	dateStr := parts[0]
	date, err := time.Parse("2006-01-02", dateStr)
	if err != nil {
		return time.Time{}, "", "", fmt.Errorf("invalid date: %v", err)
	}
	typ := ""
	note := ""
	if len(parts) == 3 {
		rest := strings.TrimSpace(parts[2])
		// Look for type in balanced parentheses
		if strings.HasPrefix(rest, "(") {
			depth := 0
			endIdx := -1
			for i, ch := range rest {
				if ch == '(' {
					depth++
				} else if ch == ')' {
					depth--
					if depth == 0 {
						endIdx = i
						break
					}
				}
			}
			if endIdx != -1 {
				typ = strings.TrimSpace(rest[1:endIdx])
				note = strings.TrimSpace(rest[endIdx+1:])
			} else {
				// Unbalanced, treat as note
				note = rest
			}
		} else {
			note = rest
		}
	}
	return date, typ, note, nil
}

// parseSetGroupLine parses a SetGroup line.
// The first field(s) are the exercise (may contain spaces, but never a number).
// The next field is the weight, then setsxreps, then optional type (in parentheses), then optional note.
func parseSetGroupLine(line string) (SetGroup, error) {
	fields := strings.Fields(line)
	if len(fields) < 3 {
		return SetGroup{}, fmt.Errorf("not enough fields for SetGroup")
	}
	// Find where the weight starts (first field with a digit)
	exerciseFields := []string{}
	weightIdx := -1
	for i, f := range fields {
		if hasDigit(f) {
			weightIdx = i
			break
		}
		exerciseFields = append(exerciseFields, f)
	}
	if weightIdx == -1 || weightIdx+2 > len(fields) {
		return SetGroup{}, fmt.Errorf("no weight or setsxreps found in SetGroup line")
	}
	exercise := strings.Join(exerciseFields, " ")
	weightField := fields[weightIdx]
	setsxrepsField := fields[weightIdx+1]

	// Parse weight and optional unit
	weight, unit, err := parseWeightAndUnit(weightField)
	if err != nil {
		return SetGroup{}, fmt.Errorf("invalid weight: %v", err)
	}
	if unit == "kg" {
		weight = weight * 2.20462 // convert to pounds
	}

	// Parse setsxreps (e.g. 5x3)
	sets, reps, err := parseSetsXReps(setsxrepsField)
	if err != nil {
		return SetGroup{}, fmt.Errorf("invalid setsxreps: %v", err)
	}

	// Remaining fields: optional type (in parentheses), then optional note
	typ := ""
	note := ""
	rest := strings.Join(fields[weightIdx+2:], " ")
	rest = strings.TrimSpace(rest)
	if strings.HasPrefix(rest, "(") {
		// Find end of type in parentheses
		depth := 0
		endIdx := -1
		for i, ch := range rest {
			if ch == '(' {
				depth++
			} else if ch == ')' {
				depth--
				if depth == 0 {
					endIdx = i
					break
				}
			}
		}
		if endIdx != -1 {
			typ = strings.TrimSpace(rest[1:endIdx])
			note = strings.TrimSpace(rest[endIdx+1:])
		} else {
			// Unbalanced, treat as note
			note = rest
		}
	} else {
		note = rest
	}

	// Build planned sets
	plannedSets := make([]Set, sets)
	for i := 0; i < sets; i++ {
		plannedSets[i] = Set{
			Weight: weight,
			Reps:   reps,
		}
	}

	return SetGroup{
		Exercise:    exercise,
		Type:        typ,
		Note:        note,
		PlannedSets: plannedSets,
		ActualSets:  nil,
	}, nil
}

func hasDigit(s string) bool {
	for _, ch := range s {
		if ch >= '0' && ch <= '9' {
			return true
		}
	}
	return false
}

// parseWeightAndUnit parses a weight field, e.g. "100kg", "225", "225lb"
func parseWeightAndUnit(field string) (float64, string, error) {
	// Find where the first non-digit or non-dot occurs
	i := 0
	for ; i < len(field); i++ {
		if (field[i] < '0' || field[i] > '9') && field[i] != '.' {
			break
		}
	}
	weightStr := field[:i]
	unit := strings.ToLower(field[i:])
	weight, err := strconv.ParseFloat(weightStr, 64)
	if err != nil {
		return 0, "", err
	}
	return weight, unit, nil
}

// parseSetsXReps parses a setsxreps field, e.g. "5x3"
func parseSetsXReps(field string) (int, int, error) {
	parts := strings.Split(field, "x")
	if len(parts) != 2 {
		return 0, 0, fmt.Errorf("expected format setsxreps, got %q", field)
	}
	sets, err := strconv.Atoi(parts[0])
	if err != nil {
		return 0, 0, fmt.Errorf("invalid sets: %v", err)
	}
	reps, err := strconv.Atoi(parts[1])
	if err != nil {
		return 0, 0, fmt.Errorf("invalid reps: %v", err)
	}
	return sets, reps, nil
}

// parseActualSetLine parses an Actual Set line (can be multiple sets separated by "-").
// The first field is set data (possibly with "-"), the rest is an optional note.
func parseActualSetLine(line string, date time.Time) ([]Set, []bool, error) {
	parts := strings.SplitN(line, " ", 2)
	setsPart := parts[0]
	note := ""
	if len(parts) == 2 {
		note = strings.TrimSpace(parts[1])
	}
	setStrs := strings.Split(setsPart, "-")
	sets := []Set{}
	weights := []bool{}
	for _, s := range setStrs {
		s = strings.TrimSpace(s)
		if s == "" {
			continue
		}
		// Parse as either "reps", "weightxreps", "weightunitxreps"
		weight := 0.0
		reps := 0
		if strings.Contains(s, "x") {
			parts := strings.SplitN(s, "x", 2)
			w, u, err := parseWeightAndUnit(parts[0])
			if err != nil {
				return nil, nil, fmt.Errorf("invalid weight in actual set: %v", err)
			}
			if u == "kg" {
				w = w * 2.20462
			}
			weights = append(weights,true)
			weight = w
			reps, err = strconv.Atoi(parts[1])
			if err != nil {
				return nil, nil, fmt.Errorf("invalid reps in actual set: %v", err)
			}
		} else {
			// Just reps, no weight
			var err error
			reps, err = strconv.Atoi(s)
			if err != nil {
				return nil, nil, fmt.Errorf("invalid reps in actual set: %v", err)
			}
			weights = append(weights,false)
		}
		sets = append(sets, Set{
			Weight: weight,
			Reps:   reps,
			Note:   "",
			Time:   date,
			RIR:    -1,
		})
	}
	if note != "" && len(sets) > 0 {
		sets[len(sets)-1].Note = note
		if strings.HasPrefix(note, "max") {
			sets[len(sets)-1].RIR = 0
		}
	}
	return sets, weights, nil
}