generate completions from tree-shaped data (nushell#683)

it might be too trivial to manually create a completion. in many
scenarios, completion is a tree-shaped structure - the current candidate
is influenced by the previous candidate.

`completion-generator` generate completion through tree-like structures
````
{a: {b: {c: {d: 1 e: 2}
````
it uses existing positional arguments as a breadcrumbs to select
candidates in tree structures

as an example, `completion-generator flare` to create completion from
online json data

`completion-generator` supports different structural expressions
````
{value: desc}
{value: { next : ...}
[a b c ...]
[{value: a, description: b, next: [...]]
{|path| ...}
````

these different structures allow any kind of nesting

Co-authored-by: nash <[email protected]>

modules/completion-generator/completion-generator.nu

@@ -0,0 +1,183 @@
+export def 'from tree' [
+ schema
+ --cmd-len(-c) = 1
+ --selector = {value: 'value', description: 'description', next: 'next'}
+] {
+ let ctx = $in
+ let argv = $ctx.0
+ | str substring 0..$ctx.1
+ | split row -r '\s+'
+ | range $cmd_len..
+ | where not ($it | str starts-with '-')
+ let menu = $argv
+ | reduce -f {schema: $schema, path: []} {|x, acc|
+ let acc = $acc | update path ($acc.path | append $x)
+ if ($x | is-empty) {
+ $acc
+ } else {
+ match ($acc.schema | describe -d | get type) {
+ record => {
+ if $x in $acc.schema {
+ $acc | merge { schema: ($acc.schema | get $x) }
+ } else {
+ $acc
+ }
+ }
+ list => {
+ let fst = $acc.schema.0? | describe -d | get type
+ if not ($fst in ['list', 'record']) {
+ $acc
+ } else {
+ let r = $acc.schema | filter {|i| ($i | get $selector.value) == $x}
+ if ($r | is-empty) {
+ $acc
+ } else {
+ $acc | merge { schema: ($r | first | get $selector.next) }
+ }
+ }
+ }
+ _ => {
+ $acc
+ }
+ }
+ }
+ | update schema {|x|
+ if ($x.schema | describe -d | get type) == 'closure' {
+ do $x.schema $x.path
+ } else {
+ $x.schema
+ }
+ }
+ }
+ match ($menu.schema | describe -d | get type) {
+ record => {
+ $menu.schema
+ | transpose k v
+ | each {|i|
+ if ($i.v | describe -d | get type) == 'string' {
+ { value: $i.k, description: $i.v }
+ } else {
+ $i.k
+ }
+ }
+ }
+ list => {
+ if ($menu.schema.0? | describe -d | get type) == 'record' {
+ $menu.schema
+ | each {|x| {$selector.value: null, $selector.description: null} | merge $x }
+ | select $selector.value $selector.description
+ | rename value description
+ } else {
+ $menu.schema
+ }
+ }
+ }
+}
+
+export def flare [...args:string@comflare] {
+ print ($args | str join ' -> ')
+}
+
+def comflare [...context] {
+ if not ('~/.cache/flare.json' | path exists) {
+ http get https://gist.githubusercontent.com/curran/d2656e98b489648ab3e2071479ced4b1/raw/9f2499d63e971c2110e52b3fa2066ebed234828c/flare-2.json
+ | to json
+ | save ~/.cache/flare.json
+ }
+ let data = open ~/.cache/flare.json
+ $context | from tree -c 2 --selector {value: name, description: value, next: children } [$data]
+}
+
+export def math [...args:string@commath] {
+ print ($args | str join ' -> ')
+}
+
+def commath [...context] {
+ $context | from tree -c 2 [
+ {
+ value: Count
+ description: closure
+ next: {|path| $path}
+ }
+ {
+ value: PureMathematics
+ next: {
+ NumberSystems: [
+ { value: NaturalNumbers, description: '1, 2, 3, 4, 5', next: [Arithmetic ] }
+ { value: Integer, description: '-2, -1, 0, 1, 2' }
+ { value: RationalNumbers, description: '-7, 1/2, 2.32' }
+ { value: RealNumbers, description: '-4pi, sqrt(2), e' }
+ { value: ComplexNumbers, description: '3, i, 4+3i, -4i' }
+ ]
+ Structures: {
+ Algebra: {
+ Equation: null
+ LinearAlgebra: [ Vector Matrices ]
+ }
+ NumberTheory: null
+ Combinatorics: [Tree Graph]
+ GroupTheory: null
+ OrderTheory: null
+ }
+ Space: {
+ Geometry: {
+ Trigonometry: null
+ FractalGeometry: null
+ }
+ Topology: null
+ MeasureTheory: null
+ DifferentialGeometry: null
+ }
+ Changes: {
+ Calculus: {
+ Differentials: null
+ Integrals: null
+ Gradients: null
+ }
+ VectorCalculus: null
+ DynamicalSystems: {
+ FluidFlows: null
+ Ecosystems: null
+ ChaosTheory: null
+ }
+ ComplexAnalysis: null
+ }
+ }
+ }
+ {
+ value: AppiledMathematics
+ next: {
+ Physics: {
+ TheoreticalPhysics: null
+ }
+ MathematicalChemistry: null
+ Biomathematics: null
+ Engineering : {
+ ControlTheory: null
+ }
+ NumericalAnalysis: null
+ GameTheory: null
+ Economics: null
+ Probability: null
+ Statistics: null
+ MathematicalFinance: null
+ Optimization: null
+ ComputerScience: {
+ MachineLearning: null
+ }
+ Cryptography: null
+ }
+ }
+ {
+ value: Foundations
+ next: {
+ FundamentalRules: { GodelIncompletenessTheorems: null }
+ MathematicalLogic: null
+ SetTheory: null
+ CategoryTheory: null
+ TheoryOfComputation: null
+ }
+ }
+ ]
+}
+