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Architecture overview

1. Layered architecture overview

Package structure (pplx_export/, ~5.6k lines of source and growing with development, excluding tests; exact line counts per wc -l):

flowchart TD
    subgraph CLI["CLI layer (entry points)"]
        CL1["cli.py — pplx-export<br/>argparse definitions + dispatch (cli.py:57)"]
        CL2["ask_cli.py — pplx-ask<br/>interactive query entry (ask_cli.py:221)"]
    end

    subgraph CMD["commands/ command layer (shared by both entries)"]
        C0["common.py<br/>account mapping / make_transport assembly<br/>cookie validation and auto-switching (common.py:93)"]
        C1["index_cmd / export_cmd / batch_cmd"]
        C2["spaces_cmd / misc_cmd / rerender_cmd"]
        C3["assets_backfill_cmd / usage_backfill_cmd<br/>search_mode_backfill_cmd / sync_deleted_cmd"]
    end

    subgraph SITES["sites/ site layer"]
        SB["base.py — SiteAdapter ABC<br/>(base.py:21)"]
        subgraph PPLX["sites/perplexity/"]
            AD["adapter.py<br/>PerplexityAdapter assembly (adapter.py:24)"]
            GQ["graphql.py<br/>APQ list pagination (graphql.py:43)"]
            RS["rest.py<br/>ThreadFetcher thread fetching (rest.py:38)"]
            PA["parsers.py<br/>single point of schema parsing (parsers.py)"]
            NM["normalize.py<br/>mode detection / math normalization (normalize.py:66,240)"]
            RD["render.py<br/>markdown rendering (render.py)"]
            AS["assets.py<br/>asset download and extension resolution (assets.py:27)"]
            AK["ask_api.py<br/>envelope / SSE / telemetry (ask_api.py)"]
            FW["fs_writer.py<br/>web_archive persistence (fs_writer.py:54)"]
            VL["variant_log.py<br/>ANSWER_VARIANT_DETECTED detection log<br/>+ jsonl registry (variant_log.py:45)"]
        end
    end

    subgraph CORE["core/ foundation layer (site-agnostic)"]
        MO["models.py domain models (models.py)"]
        ER["errors.py error types (errors.py)"]
        TH["throttle.py rate-limit backoff (throttle.py:15)"]
        ST["state.py BatchState checkpoint (state.py:63)"]
        LG["logging.py central logging (logging.py:45)"]
        CK["cookies.py + auth.py<br/>cookie sources and credentials (cookies.py:237)"]
        RL["relations.py relations graph (relations.py:200)"]
        RG["registry.py site registry (registry.py:9)"]
        subgraph HTTP["core/http/ transports"]
            TP["transport.py Transport ABC (transport.py:12)"]
            CT["cookie_transport.py<br/>urllib direct (cookie_transport.py:44)"]
            BT["bridge_transport.py<br/>WebBridge page context (bridge_transport.py:22)"]
            FB["fallback.py fallback chain [reserved · not wired]"]
            BA["browser_automation_transport.py<br/>heavyweight browser [reserved · not implemented]"]
        end
    end

    subgraph HOOKS["hooks/ extension points"]
        H1["incremental.py<br/>plan_incremental pure function (incremental.py:36)"]
        H2["relations_hook.py relations rebuild (relations_hook.py:17)"]
        H3["scheduler.py periodic schedule + cron (scheduler.py:22)"]
    end

    subgraph WRT["writers/ output abstraction"]
        WB["base.py Writer ABC (writers/base.py:17)"]
    end

    CFG["config.py — single source of site constants<br/>+ user-level config loading (account table / BOT space externalized to config.toml)"]

    CL1 --> C0
    CL2 --> C0
    C0 --> C1
    C0 --> C2
    C0 --> C3
    C1 --> AD
    C2 --> AD
    C3 --> AD
    AD --> GQ
    AD --> RS
    AD --> PA
    AD --> AS
    PA --> MO
    RD --> PA
    FW --> RD
    FW --> VL
    AD --> VL
    FW --> WB
    SB --> MO
    AD --> SB
    GQ --> TP
    RS --> TP
    AS --> TP
    AK --> CT
    CT --> TH
    CT --> ER
    C0 --> CK
    C1 --> ST
    H1 --> ST
    H2 --> RL
    RG -. "core's only import of sites:<br/>just the ABC of sites/base (registry.py:7)" .-> SB
    CFG -. "imported by all layers, zero dependencies itself" .- MO

Dependency-direction essentials (verified by grepping all imports):

  • One-way: CLI → commands → sites → core. core/ imports no Perplexity concrete implementation (no site hardcoding); the only exception is core/registry.py:7 importing the SiteAdapter ABC from sites/base.py — an interface reference, not a site reference; concrete sites are injected via register() (built-in perplexity registration in pplx_export/__init__.py:34-43).
  • config.py is the single source of site constants (domain, DEFAULT_ARCHIVE_ROOT), and loads user-level externalized config: the account tables ACCOUNT_DISPLAY_NAMES/ACCOUNT_EMAIL/ACCOUNT_UID and the BOT space come from TOML (--config > PPLX_EXPORT_CONFIG > ~/.config/pplx-export/config.toml; template config.example.toml), dicts updated in place, graceful degradation when missing; core/models.py:18 also imports it (author_folder).
  • ask_api.py is the only site-layer module that directly depends on a concrete transport implementation (imports CookieTransport and reuses its _cookie_header/_opener internals for the SSE stream, ask_api.py:23, 114-130) — SSE is outside the Transport ABC's abstraction.
  • hooks/, writers/ depend only on core/; the only implementation of writers/base.py, FilesystemWriter, lives in the site layer (fs_writer.py:54) — ABC and implementation separated.

2. Module dependency graph (real import relations)

Drawn from a full grep '^from \.' census (intra-package references omitted; all __init__.py are empty except the package root pplx_export/__init__.py, which carries the registration duty):

flowchart LR
    subgraph entry["entry points"]
        E1["cli.py"]
        E2["ask_cli.py"]
        E0["__init__.py<br/>_register_builtin (__init__.py:34)"]
    end
    subgraph cmd["commands/"]
        CM["common.py"]
        CI["index_cmd.py"]
        CE["export_cmd.py"]
        CB["batch_cmd.py"]
        CS["spaces_cmd.py"]
        CR["rerender_cmd.py"]
        CX["misc_cmd.py"]
        CA["assets_backfill_cmd.py"]
        CU["usage_backfill_cmd.py"]
        CSM["search_mode_backfill_cmd.py"]
        CSD["sync_deleted_cmd.py"]
    end
    subgraph site["sites/perplexity/"]
        SA["adapter.py"]
        SG["graphql.py"]
        SR["rest.py"]
        SP["parsers.py"]
        SN["normalize.py"]
        SE["render.py"]
        SS["assets.py"]
        SK["ask_api.py"]
        SF["fs_writer.py"]
        SV["variant_log.py"]
    end
    SBASE["sites/base.py"]
    subgraph core["core/"]
        KM["models.py"]
        KE["errors.py"]
        KT["throttle.py"]
        KS["state.py"]
        KL["logging.py"]
        KC["cookies.py"]
        KA["auth.py"]
        KR["relations.py"]
        KG["registry.py"]
        KH["http/ (transport/cookie/bridge/fallback/browser_automation)"]
    end
    subgraph hooks["hooks/"]
        HI["incremental.py"]
        HR["relations_hook.py"]
        HS["scheduler.py"]
    end
    WBS["writers/base.py"]
    CFG2["config.py"]
    TST["tests/<br/>pytest fully offline<br/>(case count per actual runs)"]

    E1 --> CM
    E1 --> CI
    E1 --> CE
    E1 --> CB
    E1 --> CS
    E1 --> CR
    E1 --> CX
    E1 --> CA
    E1 --> CU
    E1 --> CSM
    E1 --> CSD
    E1 --> KG
    E1 --> KT
    E1 --> SF
    E2 --> CM
    E2 --> CE
    E2 --> SK
    E2 --> KG
    E2 --> SF
    E0 --> KG
    E0 --> SA
    CM --> KC
    CM --> KH
    CM --> KM
    CM --> CFG2
    CB --> HI
    CB --> KS
    CB --> KT
    CB --> KE
    CB --> SF
    CB --> SV
    CE --> KS
    CR --> SP
    CR --> SE
    CR --> SA
    CR --> SV
    CSM --> SN
    CSD --> KS
    CSD --> KH
    CA --> SP
    CA --> SS
    CX --> HI
    CX --> HR
    CX --> HS
    SA --> SG
    SA --> SR
    SA --> SP
    SA --> SN
    SA --> SS
    SA --> SBASE
    SP --> KM
    SN --> KM
    SE --> SP
    SE --> SN
    SF --> SP
    SF --> SE
    SF --> SV
    SF --> WBS
    SF --> KM
    SA --> SV
    SS --> SN
    SK --> KH
    SK --> CFG2
    SG --> KH
    SR --> KH
    HI --> KS
    HR --> KR
    HS --> HI
    WBS --> KM
    WBS --> KS
    KG --> SBASE
    KH --> KT
    KH --> KE
    KM --> CFG2
    KC --> CFG2
    KA --> KH
    TST -.-> SP
    TST -.-> SE
    TST -.-> KS
    TST -.-> KT
    TST -.-> HI
    TST -.-> SS
    TST -.-> SN
    TST -.-> CR

How to read the graph:

  • Core chain: cli → commands → sites → core. No core module depends on concrete commands/sites implementations; KG → SBASE (registry → SiteAdapter ABC) is the only cross-layer reverse reference, forming a dependency-injection loop with E0's registration.
  • Aggregation inside sites/perplexity/: adapter is the facade (composing graphql/rest/parsers/ normalize/assets); render depends on parsers (source of truth for wf status classification); fs_writer depends on render + parsers + writers/base.
  • Tests tests/ live outside the package and directly import pure functions from each layer (conftest.py's render_fixture reuses commands.rerender_cmd.rerender for offline re-rendering).

19. Design principles summary

  1. Raw persisted first; everything offline-regenerable: the plain/schematized raw responses are fully written before any parsing (fs_writer.py:257-266); parsing/rendering/interruption registration can all be re-run from raw with zero network (§12), decoupling renderer evolution from historical archives.
  2. Single parsing point, tolerant of data-structure changes: field extraction is concentrated in parsers.py (the _g/_loads/to_int fault-tolerance trio); mode detection has dual redundant signals plus an all-signals-missing fallback fetch (§4) — a platform revamp's blast radius is compressed into one module.
  3. Deterministic attribution waterfall: "each background payload lands in exactly one place, never rendered twice" is guaranteed by data structures (the anchored set, used_cand single consumption, top-level-only iteration against double counting) — no heuristic time guessing; interruption semantics have five classes with one source of truth (classify_wf_status) shared by render/registration/alert paths (§5, §6).
  4. Rate-limit discipline is a safety red line: random intervals, no concurrency, 3^N backoff with a cap, auth-failure fail-fast, the ENTRY_EXPIRED terminal state, 404 never misjudged as expired (§11) — all serving the anti-ban goal of "export behavior ≈ human browsing" (an explicit user requirement).
  5. Single source of configuration + privacy externalized: site constants/default paths live only in config.py; accounts/spaces are personal privacy, externalized into user-level TOML (--config > PPLX_EXPORT_CONFIG > ~/.config/pplx-export/config.toml); multi-account cookie auto-switching is a probe loop driven by registered emails, with no manual browser operation (§9).
  6. Layered one-way dependencies: CLI → commands → sites → core, with zero site hardcoding in core and sites injected via the registry — a new site implements the five SiteAdapter methods and reuses all core facilities (sites/base.py:21-69).