{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://openpaintformat.org/schemas/technique/v1/technique.schema.json",
  "title": "Open Paint Format Technique v1 (draft)",
  "description": "A reusable technique definition: purpose, prerequisites, tools/materials, ordered instructions or parameter guidance, suitable/unsuitable paint classes, common problems and corrections, safety notes, citations, and variants. Embeds the Common document envelope. Referenced by recipes. DRAFT: not frozen; see specs/technique/v1/README.md.",
  "type": "object",
  "allOf": [
    { "$ref": "https://openpaintformat.org/schemas/common/v1/common.schema.json#/$defs/envelopeCore" },
    {
      "type": "object",
      "required": ["purpose"],
      "properties": {
        "spec": { "const": "technique" },
        "purpose": {
          "type": "string",
          "minLength": 1,
          "description": "What the technique achieves and when to use it."
        },
        "difficulty": {
          "type": "string",
          "enum": ["beginner", "intermediate", "advanced"]
        },
        "prerequisites": {
          "type": "array",
          "items": { "type": "string", "minLength": 1 },
          "description": "Skills or prior techniques a painter should have first."
        },
        "tools": {
          "type": "array",
          "items": {
            "$ref": "https://openpaintformat.org/schemas/common/v1/common.schema.json#/$defs/resource"
          }
        },
        "steps": {
          "type": "array",
          "items": { "$ref": "#/$defs/step" },
          "description": "Ordered instructions. A technique MAY provide steps, parameter guidance, or neither (prose purpose only)."
        },
        "parameters": {
          "type": "array",
          "items": { "$ref": "#/$defs/parameter" },
          "description": "Parameter guidance (e.g. thinning ratio, airbrush pressure) instead of, or alongside, ordered steps."
        },
        "suitablePaintClasses": {
          "type": "array",
          "items": { "$ref": "#/$defs/paintClass" },
          "uniqueItems": true
        },
        "unsuitablePaintClasses": {
          "type": "array",
          "items": { "$ref": "#/$defs/paintClass" },
          "uniqueItems": true
        },
        "commonProblems": {
          "type": "array",
          "items": { "$ref": "#/$defs/problem" }
        },
        "safetyNotes": {
          "type": "array",
          "items": { "type": "string", "minLength": 1 },
          "description": "Health and safety guidance where relevant."
        },
        "citations": {
          "type": "array",
          "items": { "$ref": "#/$defs/citation" }
        },
        "variants": {
          "type": "array",
          "items": { "$ref": "#/$defs/variant" }
        }
      }
    }
  ],
  "unevaluatedProperties": false,
  "$defs": {
    "paintClass": {
      "type": "string",
      "enum": [
        "acrylic",
        "oil",
        "enamel",
        "lacquer",
        "ink",
        "wash",
        "contrast",
        "technical",
        "metallic"
      ]
    },
    "step": {
      "type": "object",
      "additionalProperties": false,
      "required": ["instruction"],
      "properties": {
        "instruction": { "type": "string", "minLength": 1 },
        "note": { "type": "string" }
      }
    },
    "parameter": {
      "type": "object",
      "additionalProperties": false,
      "required": ["name", "guidance"],
      "properties": {
        "name": { "type": "string", "minLength": 1 },
        "guidance": { "type": "string", "minLength": 1 },
        "typicalValue": { "type": "string" }
      }
    },
    "problem": {
      "type": "object",
      "additionalProperties": false,
      "required": ["problem"],
      "properties": {
        "problem": { "type": "string", "minLength": 1 },
        "correction": { "type": "string" }
      }
    },
    "citation": {
      "type": "object",
      "additionalProperties": false,
      "required": ["text"],
      "properties": {
        "text": { "type": "string", "minLength": 1 },
        "url": { "type": "string", "format": "uri" }
      }
    },
    "variant": {
      "type": "object",
      "additionalProperties": false,
      "required": ["name"],
      "properties": {
        "name": { "type": "string", "minLength": 1 },
        "summary": { "type": "string" },
        "note": { "type": "string" }
      }
    }
  }
}