// Package router decides whether a task should run on a local Claude Code
// session (current Phase 1 behaviour) or be delegated to the centralized
// SecuAAS secutools AI platform (Phase 2 chantier E).
//
// The decision is driven entirely by the task's YAML frontmatter; no
// network call is performed in Decide.
package router

import "strings"

// Provider is the destination chosen for a task.
type Provider string

const (
	// ProviderClaudeCode means dispatch to a local ccl-auto tmux session
	// running Claude Code. This is the Phase 1 behaviour.
	ProviderClaudeCode Provider = "claude-code"

	// ProviderAuto means delegate to secutools and let its smart_triage
	// router pick the actual backend (GPU > Claude > Gemini fallback chain).
	ProviderAuto Provider = "auto"

	// ProviderGPU pins delegation to the in-cluster vLLM GPU pool.
	ProviderGPU Provider = "gpu"

	// ProviderGemini pins delegation to Google Gemini via secutools.
	ProviderGemini Provider = "gemini"

	// ProviderClaudeAPI pins delegation to the Anthropic API (NOT Claude
	// Code locally — this means stateless API calls billed to the secutools
	// account).
	ProviderClaudeAPI Provider = "claude-api"
)

// IsDelegated reports whether p means "submit to secutools" (i.e. not the
// local Claude Code path).
func (p Provider) IsDelegated() bool {
	switch p {
	case ProviderAuto, ProviderGPU, ProviderGemini, ProviderClaudeAPI:
		return true
	default:
		return false
	}
}

// Decision is the output of Decide: which provider to use, plus a short
// human-readable reason for logging and the /api/delegated/status endpoint.
type Decision struct {
	Provider Provider
	Reason   string
}

// Task is the slice of frontmatter fields the router cares about. It is
// intentionally narrower than the dispatcher's full TaskFrontmatter so that
// router tests don't need to import the dispatcher.
type Task struct {
	PreferredAI      string // auto | claude-code | gpu | gemini | claude-api (case-insensitive)
	AllowDelegation  bool   // default false → backward-compatible (Claude Code)
	NeedsClaudeCode  bool   // legacy bypass — forces ProviderClaudeCode
	ComplexityHint   string // low | medium | high (informational only for now)
}

// Decide returns the routing decision for the given task.
//
// Order of precedence:
//  1. needs_claude_code: true   → ProviderClaudeCode (legacy bypass, never delegate)
//  2. preferred_ai: claude-code → ProviderClaudeCode (explicit)
//  3. allow_delegation: false   → ProviderClaudeCode (default safety net)
//  4. preferred_ai parses to a delegated provider → that provider
//  5. fallback                  → ProviderAuto (let secutools smart_triage decide)
func Decide(t Task) Decision {
	if t.NeedsClaudeCode {
		return Decision{ProviderClaudeCode, "needs_claude_code=true"}
	}

	pref := strings.ToLower(strings.TrimSpace(t.PreferredAI))
	if pref == string(ProviderClaudeCode) {
		return Decision{ProviderClaudeCode, "preferred_ai=claude-code"}
	}

	if !t.AllowDelegation {
		return Decision{ProviderClaudeCode, "allow_delegation=false (default)"}
	}

	switch Provider(pref) {
	case ProviderGPU, ProviderGemini, ProviderClaudeAPI:
		return Decision{Provider(pref), "preferred_ai=" + pref}
	case ProviderAuto, "":
		return Decision{ProviderAuto, "preferred_ai=auto (smart_triage)"}
	default:
		// Unknown value: fail safe to local Claude Code so a typo doesn't
		// silently route real work to GPU.
		return Decision{ProviderClaudeCode, "unknown preferred_ai=" + pref + " → fail-safe"}
	}
}