path: root/libpanto/src/session.zig

//! On-disk session entry types and JSON serialization.
//!
//! These types are the wire format of pantograph's session log. They are
//! intentionally separate from the in-memory `Conversation`/`Message`/
//! `ContentBlock` model:
//!
//!   - The in-memory model holds only what providers need to serialize a
//!     request (`role`, `content`).
//!   - The on-disk model holds the full event-log story: provider/model
//!     used per request, assistant stop reason and usage, timestamps, and
//!     enough tree structure (`id`/`parent_id`) to allow future branching.
//!
//! Bridge functions at the bottom convert between the two. The bridge is
//! lossy by design: assistant metadata (provider/model/stop_reason/usage)
//! is recorded in entries but does NOT round-trip into the in-memory
//! conversation, because providers don't need it for request serialization.
//!
//! Format version: 1 (see `CURRENT_VERSION`). Migrations live in
//! `session_manager.zig`.

const std = @import("std");
const Allocator = std.mem.Allocator;
const Writer = std.Io.Writer;

const conversation = @import("conversation.zig");

/// Bumped whenever the on-disk format changes in a way that older readers
/// cannot tolerate. Older files are upgraded by `migrate()` on load and
/// the file is rewritten once.
pub const CURRENT_VERSION: u32 = 1;

// =============================================================================
// Header
// =============================================================================

/// First (and only) line of a session file. Metadata only — not part of
/// the entry tree (no id/parent_id).
pub const SessionHeader = struct {
    version: u32,
    id: []const u8, // UUIDv7 string, owned
    timestamp: []const u8, // ISO 8601, owned
    cwd: []const u8, // owned

    pub fn deinit(self: SessionHeader, alloc: Allocator) void {
        alloc.free(self.id);
        alloc.free(self.timestamp);
        alloc.free(self.cwd);
    }
};

// =============================================================================
// Entries
// =============================================================================

/// Fields shared by every non-header entry.
pub const EntryBase = struct {
    id: []const u8, // 8-char hex, owned
    parent_id: ?[]const u8, // owned, null for first entry
    timestamp: []const u8, // ISO 8601, owned

    pub fn deinit(self: EntryBase, alloc: Allocator) void {
        alloc.free(self.id);
        if (self.parent_id) |p| alloc.free(p);
        alloc.free(self.timestamp);
    }
};

pub const SessionEntry = union(enum) {
    message: MessageEntry,

    pub fn base(self: SessionEntry) EntryBase {
        return switch (self) {
            .message => |m| m.base,
        };
    }

    pub fn deinit(self: SessionEntry, alloc: Allocator) void {
        switch (self) {
            .message => |m| m.deinit(alloc),
        }
    }
};

pub const MessageEntry = struct {
    base: EntryBase,
    /// Recorded on user message entries (both human prompts and tool-result
    /// messages). Both are submissions to a provider API; the stamp says
    /// which one. Null on system and assistant entries.
    provider: ?[]const u8 = null, // owned
    model: ?[]const u8 = null, // owned
    message: DiskMessage,

    pub fn deinit(self: MessageEntry, alloc: Allocator) void {
        self.base.deinit(alloc);
        if (self.provider) |p| alloc.free(p);
        if (self.model) |m| alloc.free(m);
        self.message.deinit(alloc);
    }
};

pub const DiskMessageRole = enum { system, user, assistant };

pub const DiskMessage = struct {
    role: DiskMessageRole,
    content: []DiskContentBlock, // owned
    // Assistant-only metadata. Null for system/user messages.
    provider: ?[]const u8 = null, // owned
    model: ?[]const u8 = null, // owned
    stop_reason: ?[]const u8 = null, // owned
    usage: ?Usage = null,

    pub fn deinit(self: DiskMessage, alloc: Allocator) void {
        for (self.content) |block| block.deinit(alloc);
        alloc.free(self.content);
        if (self.provider) |p| alloc.free(p);
        if (self.model) |m| alloc.free(m);
        if (self.stop_reason) |s| alloc.free(s);
    }
};

/// Token usage reported by a provider for a single assistant turn.
///
/// All four input categories sum to the total prompt tokens that were
/// billed for the turn:
///   `input + cache_read + cache_write` = total prompt tokens.
///
/// `reasoning` is a **subset** of `output`, not additive — it's the
/// portion of the output that the model spent on internal reasoning
/// (OpenAI o-series, Anthropic extended thinking). Cost is computed
/// from `output` only; `reasoning` is tracked for display.
///
/// All fields are `u64` and default to 0. Providers that don't report a
/// given category leave it at 0. Future cache-tier breakdowns (e.g.
/// Anthropic's 5m vs 1h tiers) can be added as new fields without
/// breaking the format.
pub const Usage = struct {
    /// Fresh input tokens billed at the model's base input rate.
    input: u64 = 0,
    /// Output tokens billed at the model's base output rate.
    output: u64 = 0,
    /// Input tokens served from cache (typ. 0.1× base input rate on
    /// Anthropic, 0.5× on OpenAI).
    cache_read: u64 = 0,
    /// Input tokens written to a new cache entry (Anthropic only at
    /// time of writing; typ. 1.25× base input rate). OpenAI's cache
    /// hits don't bill a write premium, so this stays 0 there.
    cache_write: u64 = 0,
    /// Subset of `output` spent on reasoning. For OpenAI o-series
    /// models and Anthropic extended thinking. Display-only — cost is
    /// already accounted for via `output`.
    reasoning: u64 = 0,
};

// =============================================================================
// Content blocks
// =============================================================================

pub const DiskContentBlock = union(enum) {
    text: DiskTextBlock,
    thinking: DiskThinkingBlock,
    tool_use: DiskToolUseBlock,
    tool_result: DiskToolResultBlock,

    pub fn deinit(self: DiskContentBlock, alloc: Allocator) void {
        switch (self) {
            .text => |b| b.deinit(alloc),
            .thinking => |b| b.deinit(alloc),
            .tool_use => |b| b.deinit(alloc),
            .tool_result => |b| b.deinit(alloc),
        }
    }
};

pub const DiskTextBlock = struct {
    text: []const u8, // owned
    pub fn deinit(self: DiskTextBlock, alloc: Allocator) void {
        alloc.free(self.text);
    }
};

pub const DiskThinkingBlock = struct {
    thinking: []const u8, // owned
    /// Anthropic's opaque integrity token. Other providers do not produce
    /// one. Preserved here so resumed sessions can be sent back to
    /// Anthropic with the original thinking block intact.
    signature: ?[]const u8 = null, // owned
    pub fn deinit(self: DiskThinkingBlock, alloc: Allocator) void {
        alloc.free(self.thinking);
        if (self.signature) |s| alloc.free(s);
    }
};

pub const DiskToolUseBlock = struct {
    id: []const u8, // owned
    name: []const u8, // owned
    input: []const u8, // raw JSON bytes, owned
    pub fn deinit(self: DiskToolUseBlock, alloc: Allocator) void {
        alloc.free(self.id);
        alloc.free(self.name);
        alloc.free(self.input);
    }
};

pub const DiskToolResultBlock = struct {
    tool_use_id: []const u8, // owned
    content: []const u8, // owned
    pub fn deinit(self: DiskToolResultBlock, alloc: Allocator) void {
        alloc.free(self.tool_use_id);
        alloc.free(self.content);
    }
};

// =============================================================================
// File entry (header or entry)
// =============================================================================

pub const FileEntry = union(enum) {
    header: SessionHeader,
    entry: SessionEntry,

    pub fn deinit(self: FileEntry, alloc: Allocator) void {
        switch (self) {
            .header => |h| h.deinit(alloc),
            .entry => |e| e.deinit(alloc),
        }
    }
};

// =============================================================================
// Serialization
// =============================================================================

/// Serialize the header as a single JSON line. Caller owns returned bytes.
/// The returned slice does NOT include a trailing newline.
pub fn serializeHeader(allocator: Allocator, header: SessionHeader) ![]u8 {
    var aw: Writer.Allocating = .init(allocator);
    errdefer aw.deinit();

    var s: std.json.Stringify = .{ .writer = &aw.writer };
    try s.beginObject();
    try s.objectField("type");
    try s.write("session");
    try s.objectField("version");
    try s.write(header.version);
    try s.objectField("id");
    try s.write(header.id);
    try s.objectField("timestamp");
    try s.write(header.timestamp);
    try s.objectField("cwd");
    try s.write(header.cwd);
    try s.endObject();

    return try aw.toOwnedSlice();
}

/// Serialize an entry as a single JSON line. Caller owns returned bytes.
pub fn serializeEntry(allocator: Allocator, entry: SessionEntry) ![]u8 {
    var aw: Writer.Allocating = .init(allocator);
    errdefer aw.deinit();
    var s: std.json.Stringify = .{ .writer = &aw.writer };
    try writeEntry(&s, entry);
    return try aw.toOwnedSlice();
}

fn writeEntry(s: *std.json.Stringify, entry: SessionEntry) !void {
    switch (entry) {
        .message => |m| try writeMessageEntry(s, m),
    }
}

fn writeMessageEntry(s: *std.json.Stringify, m: MessageEntry) !void {
    try s.beginObject();
    try s.objectField("type");
    try s.write("message");
    try s.objectField("id");
    try s.write(m.base.id);
    try s.objectField("parentId");
    if (m.base.parent_id) |p| try s.write(p) else try s.write(null);
    try s.objectField("timestamp");
    try s.write(m.base.timestamp);
    // Top-level provider/model on user message entries.
    if (m.provider) |p| {
        try s.objectField("provider");
        try s.write(p);
    }
    if (m.model) |mm| {
        try s.objectField("model");
        try s.write(mm);
    }
    try s.objectField("message");
    try writeDiskMessage(s, m.message);
    try s.endObject();
}

fn writeDiskMessage(s: *std.json.Stringify, msg: DiskMessage) !void {
    try s.beginObject();
    try s.objectField("role");
    try s.write(@tagName(msg.role));
    try s.objectField("content");
    try s.beginArray();
    for (msg.content) |block| {
        try writeDiskBlock(s, block);
    }
    try s.endArray();
    if (msg.provider) |p| {
        try s.objectField("provider");
        try s.write(p);
    }
    if (msg.model) |mm| {
        try s.objectField("model");
        try s.write(mm);
    }
    if (msg.stop_reason) |sr| {
        try s.objectField("stopReason");
        try s.write(sr);
    }
    if (msg.usage) |u| {
        try s.objectField("usage");
        try s.beginObject();
        try s.objectField("input");
        try s.write(u.input);
        try s.objectField("output");
        try s.write(u.output);
        // Omit zero-valued auxiliary fields to keep older / unused
        // sessions compact. Readers default missing fields to 0, so
        // round-trip behavior is preserved.
        if (u.cache_read != 0) {
            try s.objectField("cacheRead");
            try s.write(u.cache_read);
        }
        if (u.cache_write != 0) {
            try s.objectField("cacheWrite");
            try s.write(u.cache_write);
        }
        if (u.reasoning != 0) {
            try s.objectField("reasoning");
            try s.write(u.reasoning);
        }
        try s.endObject();
    }
    try s.endObject();
}

fn writeDiskBlock(s: *std.json.Stringify, block: DiskContentBlock) !void {
    switch (block) {
        .text => |b| {
            try s.beginObject();
            try s.objectField("type");
            try s.write("text");
            try s.objectField("text");
            try s.write(b.text);
            try s.endObject();
        },
        .thinking => |b| {
            try s.beginObject();
            try s.objectField("type");
            try s.write("thinking");
            try s.objectField("thinking");
            try s.write(b.thinking);
            if (b.signature) |sig| {
                try s.objectField("signature");
                try s.write(sig);
            }
            try s.endObject();
        },
        .tool_use => |b| {
            try s.beginObject();
            try s.objectField("type");
            try s.write("toolUse");
            try s.objectField("id");
            try s.write(b.id);
            try s.objectField("name");
            try s.write(b.name);
            try s.objectField("input");
            try s.write(b.input);
            try s.endObject();
        },
        .tool_result => |b| {
            try s.beginObject();
            try s.objectField("type");
            try s.write("toolResult");
            try s.objectField("toolUseId");
            try s.write(b.tool_use_id);
            try s.objectField("content");
            try s.write(b.content);
            try s.endObject();
        },
    }
}

// =============================================================================
// Parsing
// =============================================================================

pub const ParseError = error{
    InvalidJson,
    MissingField,
    UnknownType,
    UnknownRole,
    UnknownBlockType,
} || Allocator.Error;

/// Parse one JSON line into a `FileEntry`. Caller owns all bytes.
pub fn parseLine(allocator: Allocator, line: []const u8) ParseError!FileEntry {
    var parsed = std.json.parseFromSlice(std.json.Value, allocator, line, .{}) catch {
        return error.InvalidJson;
    };
    defer parsed.deinit();
    return parseValue(allocator, parsed.value);
}

fn parseValue(allocator: Allocator, v: std.json.Value) ParseError!FileEntry {
    if (v != .object) return error.InvalidJson;
    const type_v = v.object.get("type") orelse return error.MissingField;
    if (type_v != .string) return error.MissingField;
    const t = type_v.string;
    if (std.mem.eql(u8, t, "session")) {
        return .{ .header = try parseHeaderFromObject(allocator, v.object) };
    } else if (std.mem.eql(u8, t, "message")) {
        return .{ .entry = .{ .message = try parseMessageEntry(allocator, v.object) } };
    } else {
        return error.UnknownType;
    }
}

fn parseHeaderFromObject(allocator: Allocator, obj: std.json.ObjectMap) ParseError!SessionHeader {
    const version: u32 = blk: {
        if (obj.get("version")) |vv| {
            if (vv == .integer) break :blk @intCast(vv.integer);
        }
        break :blk 1;
    };
    const id = try dupeStringField(allocator, obj, "id");
    errdefer allocator.free(id);
    const timestamp = try dupeStringField(allocator, obj, "timestamp");
    errdefer allocator.free(timestamp);
    const cwd = try dupeStringField(allocator, obj, "cwd");
    errdefer allocator.free(cwd);
    return .{
        .version = version,
        .id = id,
        .timestamp = timestamp,
        .cwd = cwd,
    };
}

fn parseMessageEntry(allocator: Allocator, obj: std.json.ObjectMap) ParseError!MessageEntry {
    const id = try dupeStringField(allocator, obj, "id");
    errdefer allocator.free(id);
    const timestamp = try dupeStringField(allocator, obj, "timestamp");
    errdefer allocator.free(timestamp);
    const parent_id: ?[]const u8 = blk: {
        const pv = obj.get("parentId") orelse break :blk null;
        if (pv == .null) break :blk null;
        if (pv != .string) return error.MissingField;
        break :blk try allocator.dupe(u8, pv.string);
    };
    errdefer if (parent_id) |p| allocator.free(p);

    const provider: ?[]const u8 = try dupeOptionalStringField(allocator, obj, "provider");
    errdefer if (provider) |p| allocator.free(p);
    const model: ?[]const u8 = try dupeOptionalStringField(allocator, obj, "model");
    errdefer if (model) |m| allocator.free(m);

    const msg_v = obj.get("message") orelse return error.MissingField;
    if (msg_v != .object) return error.MissingField;
    const msg = try parseDiskMessage(allocator, msg_v.object);

    return .{
        .base = .{ .id = id, .parent_id = parent_id, .timestamp = timestamp },
        .provider = provider,
        .model = model,
        .message = msg,
    };
}

fn parseDiskMessage(allocator: Allocator, obj: std.json.ObjectMap) ParseError!DiskMessage {
    const role_v = obj.get("role") orelse return error.MissingField;
    if (role_v != .string) return error.MissingField;
    const role = std.meta.stringToEnum(DiskMessageRole, role_v.string) orelse return error.UnknownRole;

    const content_v = obj.get("content") orelse return error.MissingField;
    if (content_v != .array) return error.MissingField;
    var content_list = try std.ArrayList(DiskContentBlock).initCapacity(allocator, content_v.array.items.len);
    errdefer {
        for (content_list.items) |b| b.deinit(allocator);
        content_list.deinit(allocator);
    }
    for (content_v.array.items) |item| {
        if (item != .object) return error.UnknownBlockType;
        const block = try parseDiskBlock(allocator, item.object);
        try content_list.append(allocator, block);
    }
    const content = try content_list.toOwnedSlice(allocator);
    errdefer {
        for (content) |b| b.deinit(allocator);
        allocator.free(content);
    }

    const provider: ?[]const u8 = try dupeOptionalStringField(allocator, obj, "provider");
    errdefer if (provider) |p| allocator.free(p);
    const model: ?[]const u8 = try dupeOptionalStringField(allocator, obj, "model");
    errdefer if (model) |m| allocator.free(m);
    const stop_reason: ?[]const u8 = try dupeOptionalStringField(allocator, obj, "stopReason");
    errdefer if (stop_reason) |s| allocator.free(s);

    var usage: ?Usage = null;
    if (obj.get("usage")) |uv| {
        if (uv == .object) {
            usage = .{
                .input = readU64(uv.object, "input"),
                .output = readU64(uv.object, "output"),
                .cache_read = readU64(uv.object, "cacheRead"),
                .cache_write = readU64(uv.object, "cacheWrite"),
                .reasoning = readU64(uv.object, "reasoning"),
            };
        }
    }

    return .{
        .role = role,
        .content = content,
        .provider = provider,
        .model = model,
        .stop_reason = stop_reason,
        .usage = usage,
    };
}

fn parseDiskBlock(allocator: Allocator, obj: std.json.ObjectMap) ParseError!DiskContentBlock {
    const type_v = obj.get("type") orelse return error.MissingField;
    if (type_v != .string) return error.MissingField;
    const t = type_v.string;
    if (std.mem.eql(u8, t, "text")) {
        const text = try dupeStringField(allocator, obj, "text");
        return .{ .text = .{ .text = text } };
    } else if (std.mem.eql(u8, t, "thinking")) {
        const text = try dupeStringField(allocator, obj, "thinking");
        errdefer allocator.free(text);
        const sig = try dupeOptionalStringField(allocator, obj, "signature");
        return .{ .thinking = .{ .thinking = text, .signature = sig } };
    } else if (std.mem.eql(u8, t, "toolUse")) {
        const id = try dupeStringField(allocator, obj, "id");
        errdefer allocator.free(id);
        const name = try dupeStringField(allocator, obj, "name");
        errdefer allocator.free(name);
        const input = try dupeStringField(allocator, obj, "input");
        return .{ .tool_use = .{ .id = id, .name = name, .input = input } };
    } else if (std.mem.eql(u8, t, "toolResult")) {
        const tuid = try dupeStringField(allocator, obj, "toolUseId");
        errdefer allocator.free(tuid);
        const content = try dupeStringField(allocator, obj, "content");
        return .{ .tool_result = .{ .tool_use_id = tuid, .content = content } };
    } else {
        return error.UnknownBlockType;
    }
}

fn readU64(obj: std.json.ObjectMap, name: []const u8) u64 {
    const v = obj.get(name) orelse return 0;
    if (v != .integer) return 0;
    if (v.integer < 0) return 0;
    return @intCast(v.integer);
}

fn dupeStringField(allocator: Allocator, obj: std.json.ObjectMap, name: []const u8) ParseError![]const u8 {
    const v = obj.get(name) orelse return error.MissingField;
    if (v != .string) return error.MissingField;
    return try allocator.dupe(u8, v.string);
}

fn dupeOptionalStringField(allocator: Allocator, obj: std.json.ObjectMap, name: []const u8) ParseError!?[]const u8 {
    const v = obj.get(name) orelse return null;
    if (v == .null) return null;
    if (v != .string) return error.MissingField;
    return try allocator.dupe(u8, v.string);
}

// =============================================================================
// Bridge between in-memory and on-disk content blocks
// =============================================================================

/// Convert an in-memory `ContentBlock` to a `DiskContentBlock`. All strings
/// are duplicated; the source block remains untouched and the resulting
/// disk block is independently owned.
pub fn contentBlockToDisk(
    allocator: Allocator,
    block: conversation.ContentBlock,
) !DiskContentBlock {
    switch (block) {
        .Text => |tb| {
            const text = try allocator.dupe(u8, tb.items);
            return .{ .text = .{ .text = text } };
        },
        .Thinking => |tb| {
            const text = try allocator.dupe(u8, tb.text.items);
            errdefer allocator.free(text);
            const sig: ?[]const u8 = if (tb.signature) |s| try allocator.dupe(u8, s) else null;
            return .{ .thinking = .{ .thinking = text, .signature = sig } };
        },
        .ToolUse => |tu| {
            const id = try allocator.dupe(u8, tu.id);
            errdefer allocator.free(id);
            const name = try allocator.dupe(u8, tu.name);
            errdefer allocator.free(name);
            const input = try allocator.dupe(u8, tu.input.items);
            return .{ .tool_use = .{ .id = id, .name = name, .input = input } };
        },
        .ToolResult => |tr| {
            const tuid = try allocator.dupe(u8, tr.tool_use_id);
            errdefer allocator.free(tuid);
            const content = try allocator.dupe(u8, tr.content.items);
            return .{ .tool_result = .{ .tool_use_id = tuid, .content = content } };
        },
    }
}

/// Convert a `DiskContentBlock` to an in-memory `ContentBlock`. Allocates
/// fresh owned buffers for every string field. The returned block is
/// independently owned.
pub fn diskContentBlockToInternal(
    allocator: Allocator,
    block: DiskContentBlock,
) !conversation.ContentBlock {
    switch (block) {
        .text => |b| {
            const tb = try conversation.textualBlockFromSlice(allocator, b.text);
            return .{ .Text = tb };
        },
        .thinking => |b| {
            const tb = try conversation.textualBlockFromSlice(allocator, b.thinking);
            errdefer {
                var mut = tb;
                mut.deinit(allocator);
            }
            const sig: ?[]const u8 = if (b.signature) |s| try allocator.dupe(u8, s) else null;
            return .{ .Thinking = .{ .text = tb, .signature = sig } };
        },
        .tool_use => |b| {
            const id = try allocator.dupe(u8, b.id);
            errdefer allocator.free(id);
            const name = try allocator.dupe(u8, b.name);
            errdefer allocator.free(name);
            const input = try conversation.textualBlockFromSlice(allocator, b.input);
            return .{ .ToolUse = .{ .id = id, .name = name, .input = input } };
        },
        .tool_result => |b| {
            const tuid = try allocator.dupe(u8, b.tool_use_id);
            errdefer allocator.free(tuid);
            const content = try conversation.textualBlockFromSlice(allocator, b.content);
            return .{ .ToolResult = .{ .tool_use_id = tuid, .content = content } };
        },
    }
}

// =============================================================================
// Tests
// =============================================================================

const testing = std.testing;

fn dupe(allocator: Allocator, s: []const u8) ![]const u8 {
    return try allocator.dupe(u8, s);
}

test "serialize/parse header round-trip" {
    const a = testing.allocator;
    const header: SessionHeader = .{
        .version = 1,
        .id = try dupe(a, "019dc5ba-53f6-71a5-ab8f-b1f8709c2572"),
        .timestamp = try dupe(a, "2026-04-25T17:40:15.990Z"),
        .cwd = try dupe(a, "/Users/travis/Code/pantograph"),
    };
    defer header.deinit(a);

    const line = try serializeHeader(a, header);
    defer a.free(line);

    var fe = try parseLine(a, line);
    defer fe.deinit(a);
    try testing.expect(fe == .header);
    try testing.expectEqual(@as(u32, 1), fe.header.version);
    try testing.expectEqualStrings(header.id, fe.header.id);
    try testing.expectEqualStrings(header.cwd, fe.header.cwd);
}

test "serialize/parse user message entry round-trip (with provider/model stamp)" {
    const a = testing.allocator;

    var content = try a.alloc(DiskContentBlock, 1);
    content[0] = .{ .text = .{ .text = try dupe(a, "hello world") } };

    const entry: SessionEntry = .{ .message = .{
        .base = .{
            .id = try dupe(a, "a1b2c3d4"),
            .parent_id = try dupe(a, "00000000"),
            .timestamp = try dupe(a, "2026-04-25T17:40:16.000Z"),
        },
        .provider = try dupe(a, "openai"),
        .model = try dupe(a, "gpt-4o"),
        .message = .{
            .role = .user,
            .content = content,
        },
    } };
    defer entry.deinit(a);

    const line = try serializeEntry(a, entry);
    defer a.free(line);

    var fe = try parseLine(a, line);
    defer fe.deinit(a);
    try testing.expect(fe == .entry);
    const got = fe.entry.message;
    try testing.expectEqualStrings("a1b2c3d4", got.base.id);
    try testing.expectEqualStrings("00000000", got.base.parent_id.?);
    try testing.expectEqualStrings("openai", got.provider.?);
    try testing.expectEqualStrings("gpt-4o", got.model.?);
    try testing.expectEqual(DiskMessageRole.user, got.message.role);
    try testing.expectEqual(@as(usize, 1), got.message.content.len);
    try testing.expectEqualStrings("hello world", got.message.content[0].text.text);
}

test "serialize/parse assistant message entry with metadata" {
    const a = testing.allocator;

    var content = try a.alloc(DiskContentBlock, 3);
    content[0] = .{ .thinking = .{
        .thinking = try dupe(a, "let me think"),
        .signature = try dupe(a, "sig-xyz"),
    } };
    content[1] = .{ .text = .{ .text = try dupe(a, "I'll check.") } };
    content[2] = .{ .tool_use = .{
        .id = try dupe(a, "tool_abc"),
        .name = try dupe(a, "bash"),
        .input = try dupe(a, "{\"command\":\"ls\"}"),
    } };

    const entry: SessionEntry = .{ .message = .{
        .base = .{
            .id = try dupe(a, "b2c3d4e5"),
            .parent_id = try dupe(a, "a1b2c3d4"),
            .timestamp = try dupe(a, "2026-04-25T17:40:17.000Z"),
        },
        .message = .{
            .role = .assistant,
            .content = content,
            .provider = try dupe(a, "anthropic"),
            .model = try dupe(a, "claude-sonnet-4-20250514"),
            .stop_reason = try dupe(a, "toolUse"),
            .usage = .{ .input = 1500, .output = 85 },
        },
    } };
    defer entry.deinit(a);

    const line = try serializeEntry(a, entry);
    defer a.free(line);

    var fe = try parseLine(a, line);
    defer fe.deinit(a);
    const got = fe.entry.message;
    try testing.expectEqual(DiskMessageRole.assistant, got.message.role);
    try testing.expectEqual(@as(usize, 3), got.message.content.len);
    try testing.expectEqualStrings("let me think", got.message.content[0].thinking.thinking);
    try testing.expectEqualStrings("sig-xyz", got.message.content[0].thinking.signature.?);
    try testing.expectEqualStrings("bash", got.message.content[2].tool_use.name);
    try testing.expectEqualStrings("{\"command\":\"ls\"}", got.message.content[2].tool_use.input);
    try testing.expectEqualStrings("anthropic", got.message.provider.?);
    try testing.expectEqualStrings("toolUse", got.message.stop_reason.?);
    try testing.expect(got.message.usage != null);
    try testing.expectEqual(@as(u64, 1500), got.message.usage.?.input);
    try testing.expectEqual(@as(u64, 85), got.message.usage.?.output);
}

test "serialize/parse tool result message entry" {
    const a = testing.allocator;

    var content = try a.alloc(DiskContentBlock, 1);
    content[0] = .{ .tool_result = .{
        .tool_use_id = try dupe(a, "tool_abc"),
        .content = try dupe(a, "file1.txt\nfile2.txt"),
    } };

    const entry: SessionEntry = .{ .message = .{
        .base = .{
            .id = try dupe(a, "c3d4e5f6"),
            .parent_id = try dupe(a, "b2c3d4e5"),
            .timestamp = try dupe(a, "2026-04-25T17:40:18.000Z"),
        },
        .provider = try dupe(a, "anthropic"),
        .model = try dupe(a, "claude-sonnet-4-20250514"),
        .message = .{
            .role = .user,
            .content = content,
        },
    } };
    defer entry.deinit(a);

    const line = try serializeEntry(a, entry);
    defer a.free(line);

    var fe = try parseLine(a, line);
    defer fe.deinit(a);
    const got = fe.entry.message;
    try testing.expectEqual(DiskMessageRole.user, got.message.role);
    try testing.expectEqualStrings("tool_abc", got.message.content[0].tool_result.tool_use_id);
    try testing.expectEqualStrings("file1.txt\nfile2.txt", got.message.content[0].tool_result.content);
    try testing.expectEqualStrings("anthropic", got.provider.?);
}

test "parse: null parentId is handled" {
    const a = testing.allocator;
    const line =
        \\{"type":"message","id":"abcdefab","parentId":null,"timestamp":"2026-04-25T17:40:00Z","message":{"role":"system","content":[{"type":"text","text":"hi"}]}}
    ;
    var fe = try parseLine(a, line);
    defer fe.deinit(a);
    try testing.expect(fe.entry.message.base.parent_id == null);
}

test "parse: malformed JSON is reported" {
    const a = testing.allocator;
    try testing.expectError(error.InvalidJson, parseLine(a, "not json"));
    try testing.expectError(error.InvalidJson, parseLine(a, "{\"type\":\"message\""));
}

test "parse: unknown entry type is reported" {
    const a = testing.allocator;
    const line =
        \\{"type":"future_entry","id":"abcdefab","parentId":null,"timestamp":"2026-04-25T17:40:00Z"}
    ;
    try testing.expectError(error.UnknownType, parseLine(a, line));
}

test "contentBlockToDisk: Text round-trips via in-memory" {
    const a = testing.allocator;

    var tb = try conversation.textualBlockFromSlice(a, "hello");
    defer tb.deinit(a);
    const block: conversation.ContentBlock = .{ .Text = tb };

    const disk = try contentBlockToDisk(a, block);
    defer disk.deinit(a);
    try testing.expectEqualStrings("hello", disk.text.text);
}

test "diskContentBlockToInternal: ToolUse preserves id/name/input" {
    const a = testing.allocator;

    const disk: DiskContentBlock = .{ .tool_use = .{
        .id = try a.dupe(u8, "tu_1"),
        .name = try a.dupe(u8, "bash"),
        .input = try a.dupe(u8, "{\"command\":\"ls\"}"),
    } };
    defer disk.deinit(a);

    var inmem = try diskContentBlockToInternal(a, disk);
    defer inmem.deinit(a);
    try testing.expectEqualStrings("tu_1", inmem.ToolUse.id);
    try testing.expectEqualStrings("bash", inmem.ToolUse.name);
    try testing.expectEqualStrings("{\"command\":\"ls\"}", inmem.ToolUse.input.items);
}

test "Usage: all five fields round-trip; zero-valued fields omitted from JSON" {
    const a = testing.allocator;

    var content = try a.alloc(DiskContentBlock, 1);
    content[0] = .{ .text = .{ .text = try dupe(a, "hi") } };

    const entry: SessionEntry = .{ .message = .{
        .base = .{
            .id = try dupe(a, "deadbeef"),
            .parent_id = null,
            .timestamp = try dupe(a, "2026-04-25T17:40:17.000Z"),
        },
        .message = .{
            .role = .assistant,
            .content = content,
            .provider = try dupe(a, "anthropic"),
            .model = try dupe(a, "claude-sonnet-4-20250514"),
            .stop_reason = try dupe(a, "stop"),
            .usage = .{
                .input = 100,
                .output = 50,
                .cache_read = 800,
                .cache_write = 200,
                .reasoning = 30,
            },
        },
    } };
    defer entry.deinit(a);

    const line = try serializeEntry(a, entry);
    defer a.free(line);

    // Every non-zero field should appear in the serialized JSON.
    try testing.expect(std.mem.indexOf(u8, line, "\"input\":100") != null);
    try testing.expect(std.mem.indexOf(u8, line, "\"output\":50") != null);
    try testing.expect(std.mem.indexOf(u8, line, "\"cacheRead\":800") != null);
    try testing.expect(std.mem.indexOf(u8, line, "\"cacheWrite\":200") != null);
    try testing.expect(std.mem.indexOf(u8, line, "\"reasoning\":30") != null);

    var fe = try parseLine(a, line);
    defer fe.deinit(a);
    const u = fe.entry.message.message.usage.?;
    try testing.expectEqual(@as(u64, 100), u.input);
    try testing.expectEqual(@as(u64, 50), u.output);
    try testing.expectEqual(@as(u64, 800), u.cache_read);
    try testing.expectEqual(@as(u64, 200), u.cache_write);
    try testing.expectEqual(@as(u64, 30), u.reasoning);
}

test "Usage: zero-valued auxiliary fields are omitted but parse back as 0" {
    const a = testing.allocator;

    var content = try a.alloc(DiskContentBlock, 1);
    content[0] = .{ .text = .{ .text = try dupe(a, "hi") } };

    const entry: SessionEntry = .{ .message = .{
        .base = .{
            .id = try dupe(a, "deadbeef"),
            .parent_id = null,
            .timestamp = try dupe(a, "2026-04-25T17:40:17.000Z"),
        },
        .message = .{
            .role = .assistant,
            .content = content,
            .usage = .{ .input = 100, .output = 50 },
        },
    } };
    defer entry.deinit(a);

    const line = try serializeEntry(a, entry);
    defer a.free(line);

    try testing.expect(std.mem.indexOf(u8, line, "cacheRead") == null);
    try testing.expect(std.mem.indexOf(u8, line, "cacheWrite") == null);
    try testing.expect(std.mem.indexOf(u8, line, "reasoning") == null);

    var fe = try parseLine(a, line);
    defer fe.deinit(a);
    const u = fe.entry.message.message.usage.?;
    try testing.expectEqual(@as(u64, 0), u.cache_read);
    try testing.expectEqual(@as(u64, 0), u.cache_write);
    try testing.expectEqual(@as(u64, 0), u.reasoning);
}

test "diskContentBlockToInternal: Thinking preserves signature" {
    const a = testing.allocator;

    const disk: DiskContentBlock = .{ .thinking = .{
        .thinking = try a.dupe(u8, "reasoning..."),
        .signature = try a.dupe(u8, "sig123"),
    } };
    defer disk.deinit(a);

    var inmem = try diskContentBlockToInternal(a, disk);
    defer inmem.deinit(a);
    try testing.expectEqualStrings("reasoning...", inmem.Thinking.text.items);
    try testing.expectEqualStrings("sig123", inmem.Thinking.signature.?);
}