// Package fetch defines the pluggable data-source interface and its
// implementations (yfinance-equivalent prices, Finnhub, RSS news).
package fetch

import (
	"context"
	"fmt"
	"time"

	"github.com/ytshih/stonks/internal/config"
)

// Quote is a single point-in-time price observation for one symbol.
type Quote struct {
	Symbol        string // ticker as passed to the fetcher, e.g. "AAPL", "BTC-USD", "GC=F"
	Label         string // human-friendly name, e.g. "Apple Inc."
	Price         float64
	ChangePercent float64 // percent change over the source's default window (usually 1 day)
	Currency      string
	Source        string // which fetcher produced this, e.g. "yfinance", "finnhub"
}

// NewsItem is a single headline/article.
type NewsItem struct {
	Title     string
	Source    string // publication or fetcher name
	URL       string
	Published time.Time
	Summary   string
}

// Result is what one fetcher call returns. The orchestrator merges Results
// from every configured fetcher before handing them to the analyzer.
type Result struct {
	Quotes []Quote
	News   []NewsItem
}

// Merge appends other's quotes and news onto r.
func (r *Result) Merge(other Result) {
	r.Quotes = append(r.Quotes, other.Quotes...)
	r.News = append(r.News, other.News...)
}

// Fetcher fetches market data and/or news for the given targets.
// Implementations should return a partial Result plus an error when only
// some data could be retrieved, rather than nothing at all — the caller
// decides whether a partial result is still worth reporting.
type Fetcher interface {
	Name() string
	Fetch(ctx context.Context, targets config.Targets) (Result, error)
}

// Constructor builds a Fetcher from its PluginConfig (name + params).
type Constructor func(cfg config.PluginConfig) (Fetcher, error)

var registry = map[string]Constructor{}

// Register makes a fetcher constructor available under name. Called from
// each fetcher implementation's init().
func Register(name string, ctor Constructor) {
	if _, exists := registry[name]; exists {
		panic(fmt.Sprintf("fetch: constructor already registered for %q", name))
	}
	registry[name] = ctor
}

// Build looks up the constructor for cfg.Name and invokes it.
func Build(cfg config.PluginConfig) (Fetcher, error) {
	ctor, ok := registry[cfg.Name]
	if !ok {
		return nil, fmt.Errorf("fetch: no fetcher registered for %q", cfg.Name)
	}
	return ctor(cfg)
}