ModelRouter/internal/core/billing_compile.go

package core

import (
	"encoding/json"
	"fmt"

	"llmsproxy/internal/config"
)

// compileBillingPrices turns a billing profile into the prices table the billing
// plugin consumes — by ASKING THE PLUGIN TO DO IT.
//
// Why the kernel does not compile prices any more (GitCode issue #1, follow-up
// direction): "how a rule becomes a price table" is billing semantics, and it
// used to live in TWO places — `internal/billing/compile.go` produced source
// entries with zero token prices, while `billing.lua`'s priceFor() applied the
// source dimension after the model dimension. Each was defensible alone; together
// they silently zeroed every request (cost 0, unpriced_reqs frozen). Splitting
// the semantics across two languages is what made that possible.
//
// So the kernel keeps only what it must own — decoding config.yaml and validating
// the DSL — and hands the PROFILE plus the source base URLs to the plugin as
// plain DATA. The plugin compiles, and the kernel injects the result through the
// existing `prices` sidecar (SetState), which also keeps price-vs-ledger
// separation intact.
//
// A plugin sandbox has no filesystem access, so "the plugin reads the config
// file" is not achievable by design; passing the decoded profile is the hook /
// interface this architecture provides instead.
func (c *Core) compileBillingPrices(profile *config.BillingProfile, lenient bool) (map[string]interface{}, []string, error) {
	if c.plugins == nil {
		return nil, nil, fmt.Errorf("plugins not loaded")
	}
	if profile == nil {
		return nil, nil, fmt.Errorf("no billing profile")
	}
	// Structs go through JSON so the Lua side receives plain data (maps/slices):
	// pushGoValue is not a struct encoder, and a silent shape mismatch here would
	// look exactly like "the plugin priced nothing".
	rawProfile, err := json.Marshal(profile)
	if err != nil {
		return nil, nil, err
	}
	var prof map[string]interface{}
	if err := json.Unmarshal(rawProfile, &prof); err != nil {
		return nil, nil, err
	}
	sources := make([]map[string]interface{}, 0, len(c.cfg.Sources))
	for _, s := range c.cfg.Sources {
		sources = append(sources, map[string]interface{}{"name": s.Name, "base_url": s.BaseURL})
	}
	out, err := c.plugins.Call("billing", "compile_prices", map[string]interface{}{
		"profile": prof, "sources": sources, "lenient": lenient,
	})
	if err != nil {
		return nil, nil, err
	}
	m, ok := out.(map[string]interface{})
	if !ok {
		return nil, nil, fmt.Errorf("billing plugin returned an unexpected shape: %T", out)
	}
	if msg, hasErr := m["error"]; hasErr {
		if e := fmt.Sprint(msg); e != "" && e != "<nil>" {
			return nil, nil, fmt.Errorf("%s", e)
		}
	}
	prices, ok := m["prices"].(map[string]interface{})
	if !ok {
		return nil, nil, fmt.Errorf("billing plugin returned no prices table")
	}
	var unmatched []string
	if arr, ok := m["unmatched_rules"].([]interface{}); ok {
		for _, v := range arr {
			unmatched = append(unmatched, fmt.Sprint(v))
		}
	}
	return prices, unmatched, nil
}

// CompileBillingPrices is compileBillingPrices for callers outside the package
// (the rules editor validates an edit before persisting it).
func (c *Core) CompileBillingPrices(profile *config.BillingProfile, lenient bool) (map[string]interface{}, []string, error) {
	return c.compileBillingPrices(profile, lenient)
}