package iace

// Minimum-distance library — Task #18.
//
// Anchor source: OSHA 29 CFR 1910 Subpart O (US Federal Public Domain,
// 17 U.S.C. §105). The values below are reproduced verbatim from the
// Federal Code; conversions to metric are mathematical and carry no
// copyright. Engineering rounding to safe-side mm values is BreakPilot's
// recommendation and labelled as such.
//
// EU norm equivalents (EN ISO 13857, EN 349, EN 13855, EN 1010) are
// referenced by identifier only — no values are reproduced, because
// DIN/Beuth retain copyright on the wording. The DINComparisonNote
// field carries a human-curated judgement on whether the EU norm is
// stricter / looser / equivalent — this is a qualitative observation
// about a publicly available document, not a copy of its text.
//
// See LICENSE_RULES.md and project_attribution_strategy.md for the
// licensing logic. The OSHA values are R1 (verbatim public domain);
// the recommended metric values are BreakPilot engineering output (R3
// own-work). DIN references are R3 identifier-only.

// MinimumDistanceUnit denotes the original unit system of the source.
type MinimumDistanceUnit string

const (
	UnitInch   MinimumDistanceUnit = "inch"
	UnitFoot   MinimumDistanceUnit = "foot"
	UnitMeter  MinimumDistanceUnit = "meter"
	UnitMM     MinimumDistanceUnit = "mm"
)

// MinimumDistance is the data contract for a single safety-distance rule.
// It can be (a) a fixed gap value, (b) a distance range, or (c) a formula
// like OSHA's Ds = 63 in/s × Ts (hand-speed constant).
type MinimumDistance struct {
	ID string `json:"id"` // MD_OSHA_001
	// Source identifier — full CFR citation or norm reference.
	SourceCFR    string `json:"source_cfr,omitempty"`    // "29 CFR §1910.217(c)(1)(i)"
	SourceTable  string `json:"source_table,omitempty"`  // "Table O-10"
	License      string `json:"license"`                 // "US Federal Public Domain"
	LicenseRule  int    `json:"license_rule"`            // 1 / 2 / 3 (see LICENSE_RULES.md)

	// Original verbatim value in the source's own unit.
	OriginalUnit    MinimumDistanceUnit `json:"original_unit"`
	OriginalValue   float64             `json:"original_value,omitempty"`
	OriginalMin     float64             `json:"original_min,omitempty"`
	OriginalMax     float64             `json:"original_max,omitempty"`

	// Exact conversion to mm — no engineering rounding.
	ExactMM    float64 `json:"exact_mm,omitempty"`
	ExactMinMM float64 `json:"exact_min_mm,omitempty"`
	ExactMaxMM float64 `json:"exact_max_mm,omitempty"`

	// Engineering-recommended metric value with safe-side rounding.
	// For minimum distances: rounded up. For maximum opening widths:
	// rounded down.
	RecommendedMM    int `json:"recommended_mm,omitempty"`
	RecommendedMinMM int `json:"recommended_min_mm,omitempty"`
	RecommendedMaxMM int `json:"recommended_max_mm,omitempty"`
	RoundingNote string `json:"rounding_note,omitempty"`

	// Optional formula constant (e.g. OSHA hand-speed 63 in/s).
	FormulaInchPerSecond float64 `json:"formula_inch_per_second,omitempty"`
	FormulaMMPerSecond   float64 `json:"formula_mm_per_second,omitempty"`
	FormulaDescription   string  `json:"formula_description,omitempty"`

	Context  string   `json:"context"`              // "Point of Operation Guarding mechanical presses"
	BodyPart string   `json:"body_part,omitempty"`  // "finger" / "hand" / "head" / "foot" / "body"
	HazardTags []string `json:"hazard_tags,omitempty"` // [crush_point, cutting_part, ...]

	// EU norm cross-reference — IDENTIFIER ONLY, no values reproduced.
	EUNormHints []EUNormHint `json:"eu_norm_hints,omitempty"`
}

// EUNormHint references an EU standard by identifier without reproducing
// any value or text from it. The DINComparisonNote is a human-curated
// qualitative judgement (stricter / equivalent / looser) — not a copy.
type EUNormHint struct {
	Norm            string `json:"norm"`             // "EN ISO 13857"
	Section         string `json:"section,omitempty"` // "Tab. 4, Schutz gegen Hineingreifen"
	DINComparisonNote string `json:"din_comparison_note,omitempty"`
}

// GetOSHAMinimumDistances returns the verbatim OSHA values for
// machine-guarding distances. All values are US Federal Public Domain
// (17 U.S.C. §105). Engineering rounding is BreakPilot's safe-side
// recommendation; OSHA values themselves are unchanged.
func GetOSHAMinimumDistances() []MinimumDistance {
	return []MinimumDistance{
		// OSHA Table O-10 row 1 — verbatim values, mathematical conversion,
		// safe-side rounded engineering recommendation.
		{
			ID:           "MD_OSHA_O10_R1",
			SourceCFR:    "29 CFR §1910.217(c)(1)(i)",
			SourceTable:  "Table O-10 row 1",
			License:      "US Federal Public Domain (17 U.S.C. §105)",
			LicenseRule:  1,
			OriginalUnit: UnitInch,
			OriginalMin:  0.5, OriginalMax: 1.5, OriginalValue: 0.25,
			ExactMinMM:   12.7, ExactMaxMM: 38.1, ExactMM: 6.35,
			RecommendedMinMM: 15, RecommendedMaxMM: 40, RecommendedMM: 6,
			RoundingNote:     "Distance auf 5-mm-Raster aufgerundet, opening auf 1-mm-Raster abgerundet (konservativ in beide Richtungen).",
			Context:          "Point-of-Operation Guarding bei mechanischen Pressen",
			BodyPart:         "finger",
			HazardTags:       []string{"crush_point", "cutting_part"},
			EUNormHints: []EUNormHint{
				{Norm: "EN ISO 13857", Section: "Tab. 4 (Hineingreifen)",
					DINComparisonNote: "Andere Methodik (Reichweitenmodell). Unabhaengig pruefen — Werte koennen abweichen."},
			},
		},
		// OSHA Table O-10 row 4 — used as a worked example in the strategy
		// discussion. Distance 3.5-5.5 in, opening max 5/8 in.
		{
			ID:           "MD_OSHA_O10_R4",
			SourceCFR:    "29 CFR §1910.217(c)(1)(i)",
			SourceTable:  "Table O-10 row 4",
			License:      "US Federal Public Domain (17 U.S.C. §105)",
			LicenseRule:  1,
			OriginalUnit: UnitInch,
			OriginalMin:  3.5, OriginalMax: 5.5, OriginalValue: 0.625,
			ExactMinMM:   88.9, ExactMaxMM: 139.7, ExactMM: 15.875,
			RecommendedMinMM: 90, RecommendedMaxMM: 140, RecommendedMM: 15,
			RoundingNote:     "Distance 88.9→90 (+1.1 mm), 139.7→140 (+0.3 mm) aufgerundet; Opening 15.875→15 (-0.875 mm) abgerundet.",
			Context:          "Point-of-Operation Guarding bei mechanischen Pressen",
			BodyPart:         "finger",
			HazardTags:       []string{"crush_point", "cutting_part"},
			EUNormHints: []EUNormHint{
				{Norm: "EN ISO 13857", Section: "Tab. 4 (Hineingreifen)",
					DINComparisonNote: "Andere Methodik (Reichweitenmodell). Compliance-Annotation pflegen."},
			},
		},
		// OSHA §1910.212(a)(5) — fan blade guards. Verbatim 1/2 inch.
		{
			ID:           "MD_OSHA_212_FAN",
			SourceCFR:    "29 CFR §1910.212(a)(5)",
			License:      "US Federal Public Domain (17 U.S.C. §105)",
			LicenseRule:  1,
			OriginalUnit: UnitInch,
			OriginalValue: 0.5,
			ExactMM:      12.7,
			RecommendedMM: 12,
			RoundingNote: "Luefterblatt-Schutzgitter: max. Spaltoeffnung 1/2 in = 12.7 mm. Konservativ auf 12 mm abgerundet.",
			Context:      "Lüfterblätter unter 7 ft (2.13 m) Höhe",
			BodyPart:     "finger",
			HazardTags:   []string{"rotating_part", "cutting_part"},
			EUNormHints: []EUNormHint{
				{Norm: "EN ISO 13857", Section: "Tab. 4",
					DINComparisonNote: "DIN-Wert pruefen."},
			},
		},
		// OSHA §1910.217 Hand-Speed Constant — formula Ds = 63 in/s × Ts
		{
			ID:           "MD_OSHA_217_PSDI",
			SourceCFR:    "29 CFR §1910.217 (Ds = 63 in/s × Ts)",
			License:      "US Federal Public Domain (17 U.S.C. §105)",
			LicenseRule:  1,
			OriginalUnit: UnitInch,
			FormulaInchPerSecond: 63.0,
			FormulaMMPerSecond:   1600.2,
			FormulaDescription: "Hand-Speed-Konstante 63 in/s ≈ 1600 mm/s. " +
				"Ds (Mindestabstand) = 63 × Ts (Stoppzeit Presse in Sekunden).",
			Context:    "PSDI Presence-Sensing Device Initiation und Two-Hand-Trip",
			BodyPart:   "hand",
			HazardTags: []string{"crush_point", "high_speed"},
			EUNormHints: []EUNormHint{
				{Norm: "EN 13855", Section: "Sicherheitsabstaende",
					DINComparisonNote: "EN 13855 nutzt andere Konstante (1600 mm/s ≈ identisch); EU-Norm unabhaengig pruefen."},
			},
		},
	}
}