import { expect, test, describe } from 'bun:test'
import {
  extractCacheMetrics,
  extractCacheReadFromRawUsage,
  resolveCacheProvider,
  formatCacheMetricsCompact,
  formatCacheMetricsFull,
  addCacheMetrics,
} from './cacheMetrics.js'

describe('extractCacheMetrics — Anthropic (firstParty/bedrock/vertex/foundry)', () => {
  test('reports read/created separately and computes hit rate over total input', () => {
    const usage = {
      input_tokens: 300,
      output_tokens: 100,
      cache_read_input_tokens: 800,
      cache_creation_input_tokens: 200,
    }
    const m = extractCacheMetrics(usage, 'anthropic')
    expect(m.supported).toBe(true)
    expect(m.read).toBe(800)
    expect(m.created).toBe(200)
    // total = fresh(300) + created(200) + read(800) = 1300
    expect(m.total).toBe(1300)
    expect(m.hitRate).toBeCloseTo(800 / 1300, 4)
  })

  test('returns cold metrics when no cache activity yet', () => {
    const m = extractCacheMetrics({ input_tokens: 500 }, 'anthropic')
    expect(m.supported).toBe(true)
    expect(m.read).toBe(0)
    expect(m.created).toBe(0)
    expect(m.hitRate).toBe(0)
  })

  test('null hit rate when usage has no input at all', () => {
    const m = extractCacheMetrics({}, 'anthropic')
    expect(m.supported).toBe(true)
    expect(m.hitRate).toBeNull()
  })
})

// NOTE: OpenAI/Codex/Kimi/DeepSeek/Gemini raw shapes are now tested through
// extractCacheReadFromRawUsage (below). extractCacheMetrics sees the
// post-shim Anthropic shape for every provider, so the tests here verify
// that the shape lookup works uniformly against the shimmed fields.

describe('extractCacheMetrics — post-shim Anthropic shape (applies to all providers)', () => {
  test('OpenAI post-shim (openai bucket) — reads Anthropic fields injected by convertChunkUsage', () => {
    // This is what cost-tracker actually sees for OpenAI upstreams: the
    // shim has already subtracted cached from prompt_tokens and moved it
    // to cache_read_input_tokens.
    const shimmed = {
      input_tokens: 800, // fresh = 2000 - 1200
      output_tokens: 300,
      cache_creation_input_tokens: 0,
      cache_read_input_tokens: 1_200,
    }
    const m = extractCacheMetrics(shimmed, 'openai')
    expect(m.supported).toBe(true)
    expect(m.read).toBe(1_200)
    expect(m.created).toBe(0)
    expect(m.total).toBe(2_000) // 800 fresh + 1200 read
    expect(m.hitRate).toBe(0.6)
  })

  test('Codex post-shim — same Anthropic shape as OpenAI', () => {
    const shimmed = {
      input_tokens: 900, // 1500 - 600
      cache_creation_input_tokens: 0,
      cache_read_input_tokens: 600,
    }
    const m = extractCacheMetrics(shimmed, 'codex')
    expect(m.read).toBe(600)
    expect(m.total).toBe(1_500)
    expect(m.hitRate).toBe(0.4)
  })

  test('Kimi post-shim — shim moved top-level cached_tokens into Anthropic field', () => {
    const shimmed = {
      input_tokens: 600, // 1000 - 400
      cache_creation_input_tokens: 0,
      cache_read_input_tokens: 400,
    }
    const m = extractCacheMetrics(shimmed, 'kimi')
    expect(m.read).toBe(400)
    expect(m.total).toBe(1_000)
    expect(m.hitRate).toBe(0.4)
  })

  test('DeepSeek post-shim — hit moved to cache_read_input_tokens, miss to input_tokens', () => {
    const shimmed = {
      input_tokens: 300, // miss
      cache_creation_input_tokens: 0,
      cache_read_input_tokens: 700, // hit
    }
    const m = extractCacheMetrics(shimmed, 'deepseek')
    expect(m.read).toBe(700)
    expect(m.total).toBe(1_000)
    expect(m.hitRate).toBe(0.7)
  })

  test('Gemini post-shim — cached_content_token_count moved to cache_read_input_tokens', () => {
    const shimmed = {
      input_tokens: 800, // 4000 - 3200
      cache_creation_input_tokens: 0,
      cache_read_input_tokens: 3_200,
    }
    const m = extractCacheMetrics(shimmed, 'gemini')
    expect(m.read).toBe(3_200)
    expect(m.total).toBe(4_000)
    expect(m.hitRate).toBe(0.8)
  })
})

describe('extractCacheReadFromRawUsage — single source of truth for shim layer', () => {
  test('Anthropic-native passthrough: cache_read_input_tokens', () => {
    expect(
      extractCacheReadFromRawUsage({ cache_read_input_tokens: 1_500 }),
    ).toBe(1_500)
  })

  test('OpenAI Chat Completions: prompt_tokens_details.cached_tokens', () => {
    expect(
      extractCacheReadFromRawUsage({
        prompt_tokens: 2_000,
        prompt_tokens_details: { cached_tokens: 1_200 },
      }),
    ).toBe(1_200)
  })

  test('Codex Responses API: input_tokens_details.cached_tokens', () => {
    expect(
      extractCacheReadFromRawUsage({
        input_tokens: 1_500,
        input_tokens_details: { cached_tokens: 600 },
      }),
    ).toBe(600)
  })

  test('Kimi / Moonshot: top-level cached_tokens', () => {
    expect(
      extractCacheReadFromRawUsage({ prompt_tokens: 1_000, cached_tokens: 400 }),
    ).toBe(400)
  })

  test('DeepSeek: prompt_cache_hit_tokens', () => {
    expect(
      extractCacheReadFromRawUsage({
        prompt_cache_hit_tokens: 700,
        prompt_cache_miss_tokens: 300,
      }),
    ).toBe(700)
  })

  test('Gemini: cached_content_token_count', () => {
    expect(
      extractCacheReadFromRawUsage({
        prompt_token_count: 4_000,
        cached_content_token_count: 3_200,
      }),
    ).toBe(3_200)
  })

  test('no cache fields at all → 0 (Copilot/Ollama/unknown shape)', () => {
    expect(extractCacheReadFromRawUsage({ prompt_tokens: 500 })).toBe(0)
  })

  test('Anthropic field wins over OpenAI field when both present', () => {
    // Shouldn't happen in practice, but if usage was double-annotated we
    // trust the Anthropic-native number (it's the more authoritative one).
    expect(
      extractCacheReadFromRawUsage({
        cache_read_input_tokens: 999,
        prompt_tokens_details: { cached_tokens: 111 },
      }),
    ).toBe(999)
  })

  test('null/undefined/non-object → 0', () => {
    expect(extractCacheReadFromRawUsage(null)).toBe(0)
    expect(extractCacheReadFromRawUsage(undefined)).toBe(0)
    expect(extractCacheReadFromRawUsage('nope' as unknown as never)).toBe(0)
  })
})

describe('extractCacheMetrics — Copilot / Ollama (unsupported)', () => {
  test('returns supported:false with all zeros and null hitRate for Copilot', () => {
    const m = extractCacheMetrics({ prompt_tokens: 1000 }, 'copilot')
    expect(m.supported).toBe(false)
    expect(m.read).toBe(0)
    expect(m.created).toBe(0)
    expect(m.hitRate).toBeNull()
  })

  test('returns supported:false for Ollama', () => {
    const m = extractCacheMetrics({ prompt_tokens: 42 }, 'ollama')
    expect(m.supported).toBe(false)
    expect(m.hitRate).toBeNull()
  })

  test('Copilot serving Claude (copilot-claude) is supported and uses Anthropic fields', () => {
    const usage = {
      input_tokens: 200,
      cache_read_input_tokens: 800,
      cache_creation_input_tokens: 100,
    }
    const m = extractCacheMetrics(usage, 'copilot-claude')
    expect(m.supported).toBe(true)
    expect(m.read).toBe(800)
    expect(m.created).toBe(100)
    expect(m.total).toBe(1_100)
  })
})

describe('extractCacheMetrics — bad/empty input', () => {
  test('null usage returns unsupported', () => {
    expect(extractCacheMetrics(null, 'anthropic').supported).toBe(false)
  })

  test('non-object usage returns unsupported', () => {
    expect(extractCacheMetrics('oops' as unknown as never, 'openai').supported).toBe(
      false,
    )
  })
})

describe('resolveCacheProvider', () => {
  test('firstParty → anthropic', () => {
    expect(resolveCacheProvider('firstParty')).toBe('anthropic')
  })
  test('bedrock/vertex/foundry → anthropic', () => {
    expect(resolveCacheProvider('bedrock')).toBe('anthropic')
    expect(resolveCacheProvider('vertex')).toBe('anthropic')
    expect(resolveCacheProvider('foundry')).toBe('anthropic')
  })
  test('github without claude hint → copilot (unsupported)', () => {
    expect(resolveCacheProvider('github')).toBe('copilot')
  })
  test('github with claude hint → copilot-claude', () => {
    expect(
      resolveCacheProvider('github', { githubNativeAnthropic: true }),
    ).toBe('copilot-claude')
  })
  test('openai with localhost / loopback → self-hosted', () => {
    // These used to return 'ollama'; the bucket is now 'self-hosted'
    // because not every local OpenAI-compatible server is Ollama
    // (could be vLLM, LM Studio, LocalAI, text-generation-webui).
    // Both buckets collapse to supported=false downstream.
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://localhost:8080/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://127.0.0.1:1234/v1' }),
    ).toBe('self-hosted')
    // Localhost:11434 hits the self-hosted branch first — 'ollama' only
    // kicks in when the :11434 port appears on a public-looking URL
    // (which would be unusual but still deserves honest classification).
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://localhost:11434/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://[::1]:5000/v1' }),
    ).toBe('self-hosted')
  })

  test('openai on RFC1918 private IP → self-hosted (pre-fix: misclassified as openai)', () => {
    // These are the exact cases the reviewer flagged. Before this fix,
    // a vLLM / LocalAI server on a LAN address fell through to the
    // 'openai' branch and /cache-stats showed '[Cache: cold]' — which
    // users read as "my cache is broken" when the provider simply
    // didn't report cache fields. Now they land in 'self-hosted' and
    // /cache-stats shows '[Cache: N/A]'.
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://192.168.1.50:8000/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://10.0.0.7:8080/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://172.20.0.3:5000/v1' }),
    ).toBe('self-hosted')
  })

  test('openai on link-local / CGNAT → self-hosted', () => {
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://169.254.169.254/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://100.64.1.5:8000/v1' }),
    ).toBe('self-hosted')
  })

  test('openai on reserved TLD (.local / .internal / .lan / .home.arpa) → self-hosted', () => {
    // Per RFC 6761 (.local/mDNS), RFC 8375 (.home.arpa), and widely
    // used .internal / .lan conventions. These never resolve publicly.
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://llm.internal:5000/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://llm.local:8080/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://vllm.home.arpa/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://box.lan:1234/v1' }),
    ).toBe('self-hosted')
  })

  test('openai on IPv6 local / link-local → self-hosted', () => {
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://[fe80::1]:8000/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://[fd12:3456::7]:8080/v1' }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'http://[fc00::1]:8080/v1' }),
    ).toBe('self-hosted')
  })

  test('IPv6 ULA prefix (fc/fd) does NOT over-match public hostnames', () => {
    // Regression guard: an early version of isLocalOrPrivateUrl checked
    // `h.startsWith('fc')` / `startsWith('fd')` without a colon guard,
    // which misclassified legitimate public hosts whose names happen to
    // begin with those letters. The fix requires a colon in the match
    // so only real IPv6 literals hit the branch.
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'https://fc-api.example.com/v1',
      }),
    ).toBe('openai')
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'https://fd-hosted.example.com/v1',
      }),
    ).toBe('openai')
    // Same goes for names that look like hex prefixes but aren't IPv6.
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'https://fcbench.net/v1',
      }),
    ).toBe('openai')
  })

  test('openai with :11434 on a public host → ollama (default-port heuristic)', () => {
    // Contrived but the heuristic should still fire — someone running
    // Ollama behind a reverse proxy with port preserved.
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'https://ollama.example.com:11434/v1',
      }),
    ).toBe('ollama')
  })

  test('openai with moonshot URL → kimi', () => {
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'https://api.moonshot.ai/v1' }),
    ).toBe('kimi')
  })
  test('openai with deepseek URL → deepseek', () => {
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'https://api.deepseek.com/v1' }),
    ).toBe('deepseek')
  })
  test('private IP beats hosted-keyword matching (self-hosted takes priority)', () => {
    // A pathological URL: a private-IP host whose path string contains
    // "deepseek". Self-hosted detection must run FIRST so the URL
    // classifies honestly — the path alone doesn't prove the upstream
    // is the real DeepSeek API.
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'http://10.0.0.5:8000/v1/deepseek-proxy',
      }),
    ).toBe('self-hosted')
  })
  test('plain openai remains openai', () => {
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'https://api.openai.com/v1' }),
    ).toBe('openai')
  })
  test('unparseable base URL falls back to substring heuristic', () => {
    // Bare host:port without a scheme is common in misconfigured env.
    // We can't URL-parse it, but we still honor the "localhost" hint so
    // a broken config doesn't silently masquerade as cache-capable.
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: 'localhost:8000' }),
    ).toBe('self-hosted')
    // An unparseable and opaque string falls through to plain 'openai'
    // (best-effort — nothing we can infer from "foo-bar-baz").
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: '???' }),
    ).toBe('openai')
  })
  test('empty base URL → plain openai', () => {
    // No hint at all: assume the canonical api.openai.com.
    expect(resolveCacheProvider('openai')).toBe('openai')
    expect(
      resolveCacheProvider('openai', { openAiBaseUrl: '' }),
    ).toBe('openai')
  })
  test('codex → codex', () => {
    expect(resolveCacheProvider('codex')).toBe('codex')
  })
  test('gemini → gemini', () => {
    expect(resolveCacheProvider('gemini')).toBe('gemini')
  })
})

describe('resolveCacheProvider — .localhost TLD (RFC 6761)', () => {
  test('subdomains of .localhost classify as self-hosted', () => {
    // Chrome, Firefox, and systemd-resolved all natively resolve
    // *.localhost to 127.0.0.1. Kubernetes Ingress and docker-compose
    // setups commonly use app.localhost, api.localhost, etc.
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'http://app.localhost:3000/v1',
      }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'http://api.localhost/v1',
      }),
    ).toBe('self-hosted')
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'http://llm.dev.localhost:8080/v1',
      }),
    ).toBe('self-hosted')
  })

  test('.localhost TLD does NOT match substring collisions', () => {
    // Guard against regressions where `localhost` would match via
    // substring rather than TLD semantics. `localhostify.com` and
    // `mylocalhost.net` must stay on the public `openai` path.
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'https://localhostify.com/v1',
      }),
    ).toBe('openai')
    expect(
      resolveCacheProvider('openai', {
        openAiBaseUrl: 'https://mylocalhost.net/v1',
      }),
    ).toBe('openai')
  })
})

describe('extractCacheMetrics — hit rate clamp', () => {
  test('hitRate is clamped to 1.0 on pathological input (read > total)', () => {
    // Defensive guard: with valid non-negative inputs the math enforces
    // read <= total, so hitRate cannot exceed 1. But an upstream shim
    // bug (e.g. reading a negative `fresh` from a future provider) could
    // break the invariant. `Math.min(1, read/total)` caps the display at
    // 100% rather than letting a `read=800 total=500` case render as
    // "hit 160%" or (worse) null, which would hide the anomaly.
    const metrics = extractCacheMetrics(
      {
        cache_read_input_tokens: 800,
        cache_creation_input_tokens: 0,
        // asNumber keeps finite negatives, so fresh = -500 → total =
        // 800 + 0 + (-500) = 300, read=800 → raw ratio 2.67, clamp to 1.
        input_tokens: -500,
      } as unknown as Record<string, unknown>,
      'anthropic',
    )
    expect(metrics.supported).toBe(true)
    expect(metrics.hitRate).toBe(1)
  })

  test('normal inputs still yield accurate fractional hit rates', () => {
    // Regression: clamp must not perturb the happy path.
    const metrics = extractCacheMetrics(
      {
        cache_read_input_tokens: 300,
        cache_creation_input_tokens: 0,
        input_tokens: 700,
      },
      'anthropic',
    )
    expect(metrics.hitRate).toBeCloseTo(0.3, 5)
  })
})

describe('extractCacheMetrics — self-hosted bucket (data-driven)', () => {
  test('vanilla self-hosted endpoint without cache fields → unsupported / N/A', () => {
    // vLLM, LocalAI, text-generation-webui, etc. emit no cache fields
    // at all. With read=created=0 we mark unsupported so the REPL shows
    // honest '[Cache: N/A]' instead of a fabricated 0%.
    const metrics = extractCacheMetrics(
      { input_tokens: 1_000, output_tokens: 200 },
      'self-hosted',
    )
    expect(metrics.supported).toBe(false)
    expect(metrics.hitRate).toBeNull()
    expect(metrics.read).toBe(0)
    expect(metrics.created).toBe(0)
  })

  test('internal reverse proxy forwarding real cache data → supported', () => {
    // Review-blocker regression guard: an enterprise setup with an
    // internal proxy on a private URL (e.g. `http://llm.internal:5000/v1`)
    // forwarding to OpenAI / Kimi / DeepSeek / Gemini WILL deliver real
    // cache fields via the shim. Pre-fix we would discard them because
    // the URL heuristic classified the endpoint as 'self-hosted'. Now
    // the data itself decides: any non-zero cache activity flows through
    // the same normalization as an OpenAI bucket.
    const shimmed = {
      input_tokens: 800, // fresh (post-shim, cached already subtracted)
      cache_read_input_tokens: 1_200, // shim extracted from upstream
      cache_creation_input_tokens: 0,
    }
    const metrics = extractCacheMetrics(shimmed, 'self-hosted')
    expect(metrics.supported).toBe(true)
    expect(metrics.read).toBe(1_200)
    expect(metrics.total).toBe(2_000)
    expect(metrics.hitRate).toBe(0.6)
  })

  test('proxy with cache_creation but zero cache_read → still supported', () => {
    // Mirror of the above for the first-call / cold-cache scenario:
    // Anthropic-compatible upstreams emit creation tokens on the first
    // request that primes the cache. Self-hosted proxy must preserve
    // that signal, not swallow it because read is still 0.
    const shimmed = {
      input_tokens: 500,
      cache_read_input_tokens: 0,
      cache_creation_input_tokens: 800,
    }
    const metrics = extractCacheMetrics(shimmed, 'self-hosted')
    expect(metrics.supported).toBe(true)
    expect(metrics.created).toBe(800)
    expect(metrics.read).toBe(0)
  })
})

describe('formatCacheMetrics — defensive null/undefined guards', () => {
  test('formatCacheMetricsCompact returns N/A for undefined input', () => {
    // Signature says `CacheMetrics` but runtime bug on a failed API
    // response could leave the caller with nothing. The formatter
    // should degrade gracefully rather than throw on `.supported`.
    expect(formatCacheMetricsCompact(undefined)).toBe('[Cache: N/A]')
    expect(formatCacheMetricsCompact(null as unknown as undefined)).toBe(
      '[Cache: N/A]',
    )
  })

  test('formatCacheMetricsFull returns N/A for undefined input', () => {
    expect(formatCacheMetricsFull(undefined)).toBe('[Cache: N/A]')
    expect(formatCacheMetricsFull(null as unknown as undefined)).toBe(
      '[Cache: N/A]',
    )
  })
})

describe('formatCacheMetricsCompact — self-hosted display paths', () => {
  test('vanilla self-hosted (no cache data) renders as N/A', () => {
    const metrics = extractCacheMetrics(
      { input_tokens: 500 },
      'self-hosted',
    )
    expect(formatCacheMetricsCompact(metrics)).toBe('[Cache: N/A]')
    expect(formatCacheMetricsFull(metrics)).toBe('[Cache: N/A]')
  })

  test('self-hosted proxy with forwarded cache data renders real metrics', () => {
    // Full display-path regression guard for the review-blocker fix:
    // the user must see the real hit rate that the upstream emitted,
    // not a silent N/A because the URL looked private.
    const metrics = extractCacheMetrics(
      {
        input_tokens: 800,
        cache_read_input_tokens: 1_200,
        cache_creation_input_tokens: 0,
      },
      'self-hosted',
    )
    expect(formatCacheMetricsCompact(metrics)).toBe('[Cache: 1.2k read • hit 60%]')
    expect(formatCacheMetricsFull(metrics)).toBe(
      '[Cache: read=1.2k created=0 hit=60%]',
    )
  })
})

describe('formatCacheMetricsCompact — snapshot-stable output', () => {
  test('supported with reads shows "k" abbreviation and hit rate', () => {
    const out = formatCacheMetricsCompact({
      read: 1_234,
      created: 0,
      total: 10_000,
      hitRate: 0.1234,
      supported: true,
    })
    expect(out).toBe('[Cache: 1.2k read • hit 12%]')
  })

  test('supported with no cache activity renders "cold"', () => {
    const out = formatCacheMetricsCompact({
      read: 0,
      created: 0,
      total: 500,
      hitRate: 0,
      supported: true,
    })
    expect(out).toBe('[Cache: cold]')
  })

  test('unsupported renders "N/A"', () => {
    const out = formatCacheMetricsCompact({
      read: 0,
      created: 0,
      total: 0,
      hitRate: null,
      supported: false,
    })
    expect(out).toBe('[Cache: N/A]')
  })

  test('small numbers render without abbreviation', () => {
    const out = formatCacheMetricsCompact({
      read: 42,
      created: 0,
      total: 100,
      hitRate: 0.42,
      supported: true,
    })
    expect(out).toBe('[Cache: 42 read • hit 42%]')
  })
})

describe('formatCacheMetricsFull — snapshot-stable output', () => {
  test('supported shows all fields', () => {
    const out = formatCacheMetricsFull({
      read: 1_234,
      created: 250,
      total: 10_000,
      hitRate: 0.1234,
      supported: true,
    })
    expect(out).toBe('[Cache: read=1.2k created=250 hit=12%]')
  })

  test('null hit rate renders n/a', () => {
    const out = formatCacheMetricsFull({
      read: 0,
      created: 0,
      total: 0,
      hitRate: null,
      supported: true,
    })
    expect(out).toBe('[Cache: read=0 created=0 hit=n/a]')
  })

  test('unsupported renders "N/A"', () => {
    const out = formatCacheMetricsFull({
      read: 0,
      created: 0,
      total: 0,
      hitRate: null,
      supported: false,
    })
    expect(out).toBe('[Cache: N/A]')
  })
})

describe('hit-rate edge cases (plan-mandated coverage)', () => {
  test('0 read / 0 created on supported provider → hitRate = 0 (not null) when total > 0', () => {
    const m = extractCacheMetrics({ input_tokens: 500 }, 'anthropic')
    expect(m.read).toBe(0)
    expect(m.created).toBe(0)
    expect(m.hitRate).toBe(0)
  })

  test('read only (no created) computes proportion correctly', () => {
    const m = extractCacheMetrics(
      { input_tokens: 0, cache_read_input_tokens: 800, cache_creation_input_tokens: 0 },
      'anthropic',
    )
    expect(m.read).toBe(800)
    expect(m.created).toBe(0)
    expect(m.total).toBe(800)
    expect(m.hitRate).toBe(1)
  })

  test('created only (first turn — no reads yet) gives 0 hit rate', () => {
    const m = extractCacheMetrics(
      {
        input_tokens: 200,
        cache_read_input_tokens: 0,
        cache_creation_input_tokens: 1_000,
      },
      'anthropic',
    )
    expect(m.read).toBe(0)
    expect(m.created).toBe(1_000)
    expect(m.total).toBe(1_200)
    expect(m.hitRate).toBe(0)
  })

  test('mixed read + created + fresh input — full denominator', () => {
    const m = extractCacheMetrics(
      {
        input_tokens: 500,
        cache_read_input_tokens: 3_000,
        cache_creation_input_tokens: 1_500,
      },
      'anthropic',
    )
    // Denominator = fresh(500) + created(1500) + read(3000) = 5_000
    // Hit = read/total = 3000 / 5000 = 0.6
    expect(m.total).toBe(5_000)
    expect(m.hitRate).toBe(0.6)
  })

  test('N/A (unsupported provider) preserves null hit-rate even with populated usage', () => {
    // Simulate a Copilot usage payload that might look like OpenAI shape —
    // we must NOT try to read it and must report supported:false.
    const m = extractCacheMetrics(
      { prompt_tokens: 5_000, prompt_tokens_details: { cached_tokens: 2_000 } },
      'copilot',
    )
    expect(m.supported).toBe(false)
    expect(m.read).toBe(0)
    expect(m.hitRate).toBeNull()
  })
})

describe('addCacheMetrics — session aggregation', () => {
  test('sums read/created/total and recomputes hit rate', () => {
    const a = {
      read: 100,
      created: 50,
      total: 300,
      hitRate: 100 / 300,
      supported: true,
    }
    const b = {
      read: 200,
      created: 0,
      total: 400,
      hitRate: 0.5,
      supported: true,
    }
    const sum = addCacheMetrics(a, b)
    expect(sum.read).toBe(300)
    expect(sum.created).toBe(50)
    expect(sum.total).toBe(700)
    expect(sum.hitRate).toBeCloseTo(300 / 700, 5)
  })

  test('unsupported + supported = supported (so we never lose honest data)', () => {
    const unsupported = {
      read: 0,
      created: 0,
      total: 0,
      hitRate: null,
      supported: false,
    }
    const supported = {
      read: 10,
      created: 0,
      total: 100,
      hitRate: 0.1,
      supported: true,
    }
    expect(addCacheMetrics(unsupported, supported)).toBe(supported)
    expect(addCacheMetrics(supported, unsupported)).toBe(supported)
  })

  test('unsupported + unsupported = unsupported', () => {
    const u = {
      read: 0,
      created: 0,
      total: 0,
      hitRate: null,
      supported: false,
    }
    const sum = addCacheMetrics(u, u)
    expect(sum.supported).toBe(false)
  })
})
