//
//  ChatViewModelPureLogicTests.swift
//  oAITests
//
// SPDX-License-Identifier: PolyForm-Noncommercial-1.0.0
// Copyright (C) 2026 Rune Olsen

import Testing
@testable import oAI

@Suite("ChatViewModel pure static helpers")
struct ChatViewModelPureLogicTests {

    // MARK: - inferProvider

    @Test("Model ID with a slash is inferred as OpenRouter")
    func infersOpenRouter() {
        #expect(ChatViewModel.inferProvider(from: "anthropic/claude-3-5-sonnet") == .openrouter)
    }

    @Test("claude- prefixed model is inferred as direct Anthropic")
    func infersAnthropic() {
        #expect(ChatViewModel.inferProvider(from: "claude-sonnet-4-5-20250929") == .anthropic)
    }

    @Test("gpt-/o1/o3/dall-e/chatgpt prefixed models are inferred as OpenAI")
    func infersOpenAI() {
        #expect(ChatViewModel.inferProvider(from: "gpt-4o") == .openai)
        #expect(ChatViewModel.inferProvider(from: "o1-preview") == .openai)
        #expect(ChatViewModel.inferProvider(from: "o3-mini") == .openai)
        #expect(ChatViewModel.inferProvider(from: "dall-e-3") == .openai)
        #expect(ChatViewModel.inferProvider(from: "chatgpt-4o-latest") == .openai)
    }

    @Test("A bare local model name with no recognized prefix falls back to Ollama")
    func fallsBackToOllama() {
        #expect(ChatViewModel.inferProvider(from: "llama3.2") == .ollama)
    }

    @Test("apple- prefixed model is inferred as Apple on-device")
    func infersAppleOnDevice() {
        #expect(ChatViewModel.inferProvider(from: "apple-on-device") == .appleOnDevice)
    }

    // MARK: - calculateCost

    @Test("Base prompt and completion cost with no cache usage")
    func calculatesBaseCost() {
        let usage = ChatResponse.Usage(promptTokens: 1_000_000, completionTokens: 1_000_000, totalTokens: 2_000_000)
        let pricing = ModelInfo.Pricing(prompt: 3.0, completion: 15.0)
        #expect(ChatViewModel.calculateCost(usage: usage, pricing: pricing) == 18.0)
    }

    @Test("Cache read tokens are charged at 0.1x the prompt rate")
    func calculatesCacheReadCost() {
        let usage = ChatResponse.Usage(
            promptTokens: 0,
            completionTokens: 0,
            totalTokens: 1_000_000,
            cacheReadInputTokens: 1_000_000
        )
        let pricing = ModelInfo.Pricing(prompt: 3.0, completion: 15.0)
        #expect(ChatViewModel.calculateCost(usage: usage, pricing: pricing) == 0.3)
    }

    @Test("Cache write tokens are charged at 1.25x the prompt rate")
    func calculatesCacheWriteCost() {
        let usage = ChatResponse.Usage(
            promptTokens: 0,
            completionTokens: 0,
            totalTokens: 1_000_000,
            cacheCreationInputTokens: 1_000_000
        )
        let pricing = ModelInfo.Pricing(prompt: 3.0, completion: 15.0)
        #expect(ChatViewModel.calculateCost(usage: usage, pricing: pricing) == 3.75)
    }

    @Test("Zero usage produces zero cost")
    func zeroUsageIsZeroCost() {
        let usage = ChatResponse.Usage(promptTokens: 0, completionTokens: 0, totalTokens: 0)
        let pricing = ModelInfo.Pricing(prompt: 3.0, completion: 15.0)
        #expect(ChatViewModel.calculateCost(usage: usage, pricing: pricing) == 0.0)
    }

    // MARK: - draftFingerprint

    @Test("Identical message content produces the same fingerprint")
    func draftFingerprintStableForSameContent() {
        let messages = [
            Message(role: .user, content: "Hello there"),
            Message(role: .assistant, content: "Hi! How can I help?")
        ]
        #expect(ChatViewModel.draftFingerprint(for: messages) == ChatViewModel.draftFingerprint(for: messages))
    }

    @Test("Changed message content produces a different fingerprint")
    func draftFingerprintChangesWithContent() {
        let before = [Message(role: .user, content: "Hello there")]
        let after = [Message(role: .user, content: "Hello there"), Message(role: .assistant, content: "Hi!")]
        #expect(ChatViewModel.draftFingerprint(for: before) != ChatViewModel.draftFingerprint(for: after))
    }

    @Test("Empty message list has a stable fingerprint")
    func draftFingerprintEmptyIsStable() {
        #expect(ChatViewModel.draftFingerprint(for: []) == ChatViewModel.draftFingerprint(for: []))
    }
}