// Package spotted answers what effect names other keyboards' definitions have
// been seen to use for a given effect ID.
//
// It is evidence, not an answer, and the difference is the point. No definition
// file, firmware image, protocol query or version number yields the spelling of
// an effect for a board whose manufacturer never wrote one down, and the README
// says so instead of filling the gap. What can be measured is what the boards
// that did write theirs call the same number — and the measurement this package
// carries shows why that is not a name: of the 122 definitions in VIA's
// collection that file an rgb_matrix effect list, 95 are one manufacturer's, so
// the most frequent spelling of nearly every ID is one house style. Worse, the
// disagreement where it exists is not about spelling. Effect 7 is
// `rainbow_moving_chevron` on 95 boards and `cycle_out_in` on 8, which are
// different effects, not two ways of writing one.
//
// So every name here travels with the number of boards that wrote it and the
// manufacturer behind most of them, and a caller that shows one to a user has to
// show those too. A name without them is a guess wearing a count.
package spotted

import (
	_ "embed"
	"encoding/json"
	"strconv"
	"sync"
)

//go:embed spotted.json
var raw []byte

// Candidate is one spelling seen for an effect ID, and how many boards wrote it.
type Candidate struct {
	Name  string `json:"name"`
	Count int    `json:"count"`
}

// Observation is what was seen for one effect ID under one value key.
type Observation struct {
	// Boards is how many definitions listed this ID at all. It is the sample
	// size: a name backed by four boards is worth less than one backed by a
	// hundred and a half, and that difference is not visible anywhere else.
	Boards int `json:"boards"`
	// Candidates are the spellings, most frequent first.
	Candidates []Candidate `json:"candidates"`
	// TopVendor is the manufacturer behind the most of them and TopVendorCount how
	// many. A name whose share is nearly all one vendor is that vendor's
	// spelling, which is what this says.
	TopVendor      string `json:"topVendor,omitempty"`
	TopVendorCount int    `json:"topVendorCount,omitempty"`
}

// report is the generated measurement. Its shape is written by
// internal/spotted/generate and must not be hand-edited.
type report struct {
	Source      string `json:"source"`
	Commit      string `json:"commit"`
	Definitions int    `json:"definitions"`
	// EffectBoards is how many of Definitions carried an effect list with names.
	// The gap to Definitions is the size of the problem: the rest either name one
	// of VIA's built-in menus or do not light up at all.
	EffectBoards int                               `json:"effectBoards"`
	Effects      map[string]map[string]Observation `json:"effects"`
}

var (
	once   sync.Once
	loaded *report
	parse  error
)

func get() (*report, error) {
	once.Do(func() {
		loaded = &report{}
		parse = json.Unmarshal(raw, loaded)
	})
	return loaded, parse
}

// Candidates returns what has been seen for an effect ID under a VIA value key,
// and whether anything was. An ID nothing was seen for is not an error: most IDs
// above 23 are unobserved, because only a handful of boards go that far.
func Candidates(valueKey string, id int) (Observation, bool) {
	rep, err := get()
	if err != nil {
		return Observation{}, false
	}
	byID, ok := rep.Effects[valueKey]
	if !ok {
		return Observation{}, false
	}
	obs, ok := byID[strconv.Itoa(id)]
	return obs, ok
}

// Provenance describes what the measurement is a measurement of, for a caller to
// print: where it came from, which commit, and how much of the collection
// carried an effect list at all.
type Provenance struct {
	Source       string
	Commit       string
	Definitions  int
	EffectBoards int
}

// About reports where the measurement came from. A collection that moves means a
// name in it ages, and the commit is what says how far.
func About() (Provenance, bool) {
	rep, err := get()
	if err != nil {
		return Provenance{}, false
	}
	return Provenance{
		Source:       rep.Source,
		Commit:       rep.Commit,
		Definitions:  rep.Definitions,
		EffectBoards: rep.EffectBoards,
	}, true
}