JSON Patch

use json_patch.qweruse json_diff, json_patch_apply from json_patch      // Quillo 0.6: only these

json-patch = "3"

// A PATCH endpoint that takes merge patches, an undo built from the diff, and a change history.////   quillo run json_patch.qwe      then open http://localhost:8080/historyuse "json_patch.qwer"let product = { sku: "B7", name: "Blue mug", price: 12.5, tags: ["kitchen", "blue"], stock: { amsterdam: 4, london: 0 } }route PATCH /products/b7 = json_merge(product, request.json)route GET /history {    let after = json_merge(product, { price: 11.0, tags: ["kitchen", "blue", "sale"], stock: { london: 12 }, name: null })    let change = json_diff(product, after)?    let undo = json_diff(after, product)?    { after, change, undone: json_patch_apply(after, undo)? == product }}route GET /apply {    let patch = [{ op: "test", path: "/price", value: 12.5 }, { op: "replace", path: "/price", value: 9.99 }, { op: "add", path: "/tags/-", value: "gift" }]    { patched: json_patch_apply(product, patch)?, stale: json_patch_apply(json_merge(product, { price: 13 }), patch).error }}

//! JSON Patch (RFC 6902) and JSON Merge Patch (RFC 7396): the difference between two values as a list of operations, and patches applied, for PATCH endpoints, undo and audit trails.//! version: 1.0.0//!//! [dependencies]//! json-patch = "3"use serde_json::Value;/// The RFC 6902 patch that turns `before` into `after`: a list of `{ op, path, value }` (`add`, `remove`, `replace`), empty when they are equal.pub fn json_diff(before: serde_json::Value, after: serde_json::Value) -> Result<Value, String> {    serde_json::to_value(json_patch::diff(&before, &after)).map_err(|e| e.to_string())}/// `value` with an RFC 6902 `patch` applied (`add`, `remove`, `replace`, `move`, `copy` and `test`). All or nothing: when one/// operation fails (a path that is not there, a `test` that does not hold), the error names it and nothing is applied.pub fn json_patch_apply(value: serde_json::Value, patch: serde_json::Value) -> Result<Value, String> {    let p: json_patch::Patch = serde_json::from_value(patch).map_err(|e| format!("not a JSON Patch (a list of {{ op, path, ... }}): {}", e))?;    if p.0.len() > 10_000 {        return Err("at most 10,000 operations".into());    }    let mut v = value;    json_patch::patch(&mut v, &p).map_err(|e| e.to_string())?;    Ok(v)}/// `value` with an RFC 7396 merge patch applied: the patch's keys replace the value's, `null` removes a key, maps merge all/// the way down, lists are replaced whole. What most PATCH endpoints take.pub fn json_merge(value: serde_json::Value, merge_patch: serde_json::Value) -> Value {    let mut v = value;    json_patch::merge(&mut v, &merge_patch);    v}