package source

import (
	"fmt"
	"strings"
)

func ValidateDocument(doc *SourceDocument) error {
	if doc == nil {
		return fmt.Errorf("source document must not be nil")
	}
	if isBlank(doc.ID) {
		return fmt.Errorf("source document id must not be empty")
	}
	if hasSurroundingWhitespace(doc.ID) {
		return fmt.Errorf("source document id %q must not contain leading or trailing whitespace", doc.ID)
	}
	if isBlank(doc.Kind) {
		return fmt.Errorf("source document kind must not be empty")
	}
	if isBlank(doc.Format) {
		return fmt.Errorf("source document format must not be empty")
	}
	if isBlank(doc.Digest) {
		return fmt.Errorf("source document digest must not be empty")
	}
	if len(doc.Units) == 0 {
		return fmt.Errorf("source document units must not be empty")
	}

	seenUnitIDs := make(map[int]struct{}, len(doc.Units))
	for i, unit := range doc.Units {
		if unit.ID <= 0 {
			return fmt.Errorf("source unit[%d].id must be positive", i)
		}
		if isBlank(unit.Kind) {
			return fmt.Errorf("source unit[%d].kind must not be empty", i)
		}
		if isBlank(unit.Text) {
			return fmt.Errorf("source unit[%d].text must not be empty", i)
		}
		if _, ok := seenUnitIDs[unit.ID]; ok {
			return fmt.Errorf("source unit id %d is duplicated", unit.ID)
		}
		seenUnitIDs[unit.ID] = struct{}{}
	}
	for i, unit := range doc.Units {
		if err := ValidateRef(doc, unit.Ref); err != nil {
			return fmt.Errorf("source unit[%d].ref: %w", i, err)
		}
		if unit.Ref.StartUnitID != unit.ID || unit.Ref.EndUnitID != unit.ID {
			return fmt.Errorf("source unit[%d].ref must identify source unit id %d", i, unit.ID)
		}
	}

	return nil
}

func ValidateRef(doc *SourceDocument, ref SourceRef) error {
	if doc == nil {
		return fmt.Errorf("source document must not be nil")
	}
	if isBlank(ref.SourceID) {
		return fmt.Errorf("source ref source_id must not be empty")
	}
	if hasSurroundingWhitespace(ref.SourceID) {
		return fmt.Errorf("source ref source_id %q must not contain leading or trailing whitespace", ref.SourceID)
	}
	if ref.StartUnitID <= 0 {
		return fmt.Errorf("source ref start_unit_id must be positive")
	}
	if ref.EndUnitID <= 0 {
		return fmt.Errorf("source ref end_unit_id must be positive")
	}
	if ref.SourceID != doc.ID {
		return fmt.Errorf("source ref source_id %q does not match document id %q", ref.SourceID, doc.ID)
	}

	startIndex, ok := UnitIndex(doc, ref.StartUnitID)
	if !ok {
		return fmt.Errorf("source ref start_unit_id %d was not found", ref.StartUnitID)
	}
	endIndex, ok := UnitIndex(doc, ref.EndUnitID)
	if !ok {
		return fmt.Errorf("source ref end_unit_id %d was not found", ref.EndUnitID)
	}
	if startIndex > endIndex {
		return fmt.Errorf("source ref start_unit_id %d appears after end_unit_id %d", ref.StartUnitID, ref.EndUnitID)
	}

	return nil
}

func UnitIndex(doc *SourceDocument, unitID int) (int, bool) {
	if doc == nil {
		return 0, false
	}
	for i, unit := range doc.Units {
		if unit.ID == unitID {
			return i, true
		}
	}
	return 0, false
}

func isBlank(value string) bool {
	return strings.TrimSpace(value) == ""
}

func hasSurroundingWhitespace(value string) bool {
	return strings.TrimSpace(value) != value
}