work

8 files changed, 517 insertions, 0 deletions

diff --git a/libpanto/src/agent.zig b/libpanto/src/agent.zig
new file mode 100644
index 0000000..7ebc058
--- /dev/null
+++ b/libpanto/src/agent.zig
@@ -0,0 +1,23 @@
+const std = @import("std");
+const provider = @import("provider.zig");
+const conversation = @import("conversation.zig");
+
+pub const Agent = struct {
+    provider: provider.Provider,
+    allocator: std.mem.Allocator,
+
+    pub fn init(allocator: std.mem.Allocator, prov: provider.Provider) Agent {
+        return .{
+            .provider = prov,
+            .allocator = allocator,
+        };
+    }
+
+    pub fn runStep(self: Agent, conv: *conversation.Conversation, receiver: *provider.Receiver) !void {
+        try self.provider.streamStep(conv, receiver);
+    }
+
+    pub fn deinit(self: Agent) void {
+        self.provider.deinit();
+    }
+};
diff --git a/libpanto/src/config.zig b/libpanto/src/config.zig
new file mode 100644
index 0000000..295f2c6
--- /dev/null
+++ b/libpanto/src/config.zig
@@ -0,0 +1,25 @@
+pub const APIStyle = enum {
+    anthropic,
+};
+
+pub const Config = struct {
+    api_style: APIStyle,
+    api_key: []const u8,
+    base_url: []const u8,
+    model: []const u8,
+};
+
+const t = @import("std").testing;
+
+test "Config - construct with all fields" {
+    const cfg = Config{
+        .api_style = .anthropic,
+        .api_key = "sk-ant-test",
+        .base_url = "https://api.anthropic.com",
+        .model = "claude-sonnet-4-20250514",
+    };
+    try t.expectEqual(APIStyle.anthropic, cfg.api_style);
+    try t.expectEqualStrings("sk-ant-test", cfg.api_key);
+    try t.expectEqualStrings("https://api.anthropic.com", cfg.base_url);
+    try t.expectEqualStrings("claude-sonnet-4-20250514", cfg.model);
+}
diff --git a/libpanto/src/conversation.zig b/libpanto/src/conversation.zig
new file mode 100644
index 0000000..0e9a4e9
--- /dev/null
+++ b/libpanto/src/conversation.zig
@@ -0,0 +1,185 @@
+const std = @import("std");
+const Allocator = std.mem.Allocator;
+
+/// A streaming text buffer used by content blocks.
+/// Thin alias over ArrayList(u8) — amortized O(1) appends,
+/// no O(n²) re-copying.
+pub const TextualBlock = std.ArrayList(u8);
+
+/// Create a TextualBlock with initial content (copies the slice).
+pub fn textualBlockFromSlice(alloc: Allocator, slice: []const u8) !TextualBlock {
+    var buf: TextualBlock = .empty;
+    try buf.appendSlice(alloc, slice);
+    return buf;
+}
+
+pub const ToolUseBlock = struct {
+    id: []const u8,
+    name: []const u8,
+    input: TextualBlock = .empty,
+
+    pub fn deinit(self: *ToolUseBlock, alloc: Allocator) void {
+        alloc.free(self.id);
+        alloc.free(self.name);
+        self.input.deinit(alloc);
+    }
+};
+
+pub const ToolResultBlock = struct {
+    tool_use_id: []const u8,
+    content: TextualBlock = .empty,
+
+    pub fn deinit(self: *ToolResultBlock, alloc: Allocator) void {
+        alloc.free(self.tool_use_id);
+        self.content.deinit(alloc);
+    }
+};
+
+pub const ContentBlock = union(enum) {
+    Text: TextualBlock,
+    Thinking: TextualBlock,
+    ToolUse: ToolUseBlock,
+    ToolResult: ToolResultBlock,
+
+    pub fn deinit(self: *ContentBlock, alloc: Allocator) void {
+        switch (self.*) {
+            inline else => |*b| b.deinit(alloc),
+        }
+    }
+};
+
+pub const MessageRole = enum {
+    system,
+    user,
+    assistant,
+};
+
+pub const Message = struct {
+    role: MessageRole,
+    content: std.ArrayList(ContentBlock) = .empty,
+
+    pub fn deinit(self: *Message, alloc: Allocator) void {
+        for (self.content.items) |*block| {
+            block.deinit(alloc);
+        }
+        self.content.deinit(alloc);
+    }
+};
+
+pub const Conversation = struct {
+    messages: std.ArrayList(Message) = .empty,
+    allocator: Allocator,
+
+    pub fn init(allocator: Allocator) Conversation {
+        return .{
+            .allocator = allocator,
+        };
+    }
+
+    pub fn addSystemMessage(self: *Conversation, text: []const u8) !void {
+        const tb = try textualBlockFromSlice(self.allocator, text);
+        var content: std.ArrayList(ContentBlock) = .empty;
+        try content.append(self.allocator, .{ .Text = tb });
+        try self.messages.append(self.allocator, .{
+            .role = .system,
+            .content = content,
+        });
+    }
+
+    pub fn addUserMessage(self: *Conversation, text: []const u8) !void {
+        const tb = try textualBlockFromSlice(self.allocator, text);
+        var content: std.ArrayList(ContentBlock) = .empty;
+        try content.append(self.allocator, .{ .Text = tb });
+        try self.messages.append(self.allocator, .{
+            .role = .user,
+            .content = content,
+        });
+    }
+
+    /// Append an assistant message. Ownership of the blocks is transferred
+    /// to the conversation; the caller must not deinit them after this call.
+    pub fn addAssistantMessage(self: *Conversation, blocks: []const ContentBlock) !void {
+        var content: std.ArrayList(ContentBlock) = .empty;
+        try content.ensureTotalCapacity(self.allocator, blocks.len);
+        for (blocks) |block| {
+            content.appendAssumeCapacity(block);
+        }
+        try self.messages.append(self.allocator, .{
+            .role = .assistant,
+            .content = content,
+        });
+    }
+
+    pub fn deinit(self: *Conversation) void {
+        for (self.messages.items) |*msg| {
+            msg.deinit(self.allocator);
+        }
+        self.messages.deinit(self.allocator);
+    }
+};
+
+test "Conversation - add messages and verify content" {
+    const allocator = std.testing.allocator;
+
+    var conv = Conversation.init(allocator);
+    defer conv.deinit();
+
+    try conv.addSystemMessage("You are a helpful assistant.");
+    try conv.addUserMessage("Hello!");
+    try conv.addAssistantMessage(&.{
+        .{ .Text = try textualBlockFromSlice(allocator, "Hi there!") },
+    });
+
+    try std.testing.expectEqual(@as(usize, 3), conv.messages.items.len);
+
+    try std.testing.expectEqual(MessageRole.system, conv.messages.items[0].role);
+    try std.testing.expectEqualStrings(
+        "You are a helpful assistant.",
+        conv.messages.items[0].content.items[0].Text.items,
+    );
+
+    try std.testing.expectEqual(MessageRole.user, conv.messages.items[1].role);
+    try std.testing.expectEqualStrings("Hello!", conv.messages.items[1].content.items[0].Text.items);
+
+    try std.testing.expectEqual(MessageRole.assistant, conv.messages.items[2].role);
+    try std.testing.expectEqualStrings("Hi there!", conv.messages.items[2].content.items[0].Text.items);
+}
+
+test "TextualBlock - incremental append" {
+    const allocator = std.testing.allocator;
+
+    var tb = TextualBlock.empty;
+    defer tb.deinit(allocator);
+
+    try tb.appendSlice(allocator, "Hello");
+    try tb.appendSlice(allocator, " world");
+    try std.testing.expectEqualStrings("Hello world", tb.items);
+}
+
+test "Conversation - deinit frees without leaks" {
+    const allocator = std.testing.allocator;
+
+    var conv = Conversation.init(allocator);
+    try conv.addSystemMessage("system");
+    try conv.addUserMessage("user message");
+    try conv.addAssistantMessage(&.{
+        .{ .Text = try textualBlockFromSlice(allocator, "response") },
+    });
+    conv.deinit();
+}
+
+test "ContentBlock - Thinking variant" {
+    const allocator = std.testing.allocator;
+
+    var conv = Conversation.init(allocator);
+    defer conv.deinit();
+
+    try conv.addAssistantMessage(&.{
+        .{ .Thinking = try textualBlockFromSlice(allocator, "hmm...") },
+        .{ .Text = try textualBlockFromSlice(allocator, "answer") },
+    });
+
+    try std.testing.expectEqual(@as(usize, 2), conv.messages.items[0].content.items.len);
+    try std.testing.expectEqualStrings("hmm...", conv.messages.items[0].content.items[0].Thinking.items);
+    try std.testing.expectEqualStrings("answer", conv.messages.items[0].content.items[1].Text.items);
+}
diff --git a/libpanto/src/json.zig b/libpanto/src/json.zig
new file mode 100644
index 0000000..542391e
--- /dev/null
+++ b/libpanto/src/json.zig
@@ -0,0 +1,4 @@
+// Serialization helpers — model → wire JSON, deltas → ContentBlocks.
+// Implementation pending; this module will handle:
+//   1. Serialize Conversation → OpenAI request body JSON
+//   2. Parse SSE chunk deltas → ContentBlock updates
diff --git a/libpanto/src/provider.zig b/libpanto/src/provider.zig
new file mode 100644
index 0000000..8d6eea5
--- /dev/null
+++ b/libpanto/src/provider.zig
@@ -0,0 +1,66 @@
+const std = @import("std");
+const conversation = @import("conversation.zig");
+
+pub const ContentBlockType = enum {
+    Text,
+    Thinking,
+    ToolUse,
+    ToolResult,
+};
+
+pub const BlockMeta = struct {
+    /// Only populated for ToolUse blocks. Null for Text/Thinking.
+    tool_id: ?[]const u8 = null,
+    tool_name: ?[]const u8 = null,
+};
+
+pub const ReceiverVTable = struct {
+    onMessageStart: *const fn (*anyopaque, conversation.MessageRole) void,
+    onBlockStart: *const fn (*anyopaque, ContentBlockType, usize, ?BlockMeta) void,
+    onContentDelta: *const fn (*anyopaque, usize, []const u8) void,
+    onBlockComplete: *const fn (*anyopaque, usize, conversation.ContentBlock) void,
+    onMessageComplete: *const fn (*anyopaque, conversation.Message) void,
+};
+
+pub const Receiver = struct {
+    ptr: *anyopaque,
+    vtable: *const ReceiverVTable,
+
+    pub fn onMessageStart(self: Receiver, role: conversation.MessageRole) void {
+        self.vtable.onMessageStart(self.ptr, role);
+    }
+
+    pub fn onBlockStart(self: Receiver, block_type: ContentBlockType, index: usize, meta: ?BlockMeta) void {
+        self.vtable.onBlockStart(self.ptr, block_type, index, meta);
+    }
+
+    pub fn onContentDelta(self: Receiver, block_index: usize, delta: []const u8) void {
+        self.vtable.onContentDelta(self.ptr, block_index, delta);
+    }
+
+    pub fn onBlockComplete(self: Receiver, block_index: usize, block: conversation.ContentBlock) void {
+        self.vtable.onBlockComplete(self.ptr, block_index, block);
+    }
+
+    pub fn onMessageComplete(self: Receiver, message: conversation.Message) void {
+        self.vtable.onMessageComplete(self.ptr, message);
+    }
+};
+
+pub const ProviderVTable = struct {
+    streamStep: *const fn (*anyopaque, *conversation.Conversation, *Receiver) anyerror!void,
+    deinit: *const fn (*anyopaque) void,
+};
+
+pub const Provider = struct {
+    ptr: *anyopaque,
+    vtable: *const ProviderVTable,
+
+    pub fn streamStep(self: Provider, conv: *conversation.Conversation, receiver: *Receiver) anyerror!void {
+        return self.vtable.streamStep(self.ptr, conv, receiver);
+    }
+
+    pub fn deinit(self: Provider) void {
+        self.vtable.deinit(self.ptr);
+    }
+};
diff --git a/libpanto/src/provider_openai.zig b/libpanto/src/provider_openai.zig
new file mode 100644
index 0000000..c459a9e
--- /dev/null
+++ b/libpanto/src/provider_openai.zig
@@ -0,0 +1,6 @@
+// OpenAI-compatible provider implementation.
+// Implementation pending; this module will:
+//   - Convert Conversation → OpenAI wire JSON
+//   - Make HTTP POST with stream: true
+//   - Parse SSE events, drive block boundary state machine
+//   - Call the full Receiver callback sequence
diff --git a/libpanto/src/root.zig b/libpanto/src/root.zig
new file mode 100644
index 0000000..72ceb97
--- /dev/null
+++ b/libpanto/src/root.zig
@@ -0,0 +1,9 @@
+pub const conversation = @import("conversation.zig");
+pub const provider = @import("provider.zig");
+pub const agent = @import("agent.zig");
+pub const config = @import("config.zig");
+pub const sse = @import("sse.zig");
+
+// Internal modules — not re-exported as public API
+// pub const json = @import("json.zig");
+// pub const provider_openai = @import("provider_openai.zig");
diff --git a/libpanto/src/sse.zig b/libpanto/src/sse.zig
new file mode 100644
index 0000000..150c3ea
--- /dev/null
+++ b/libpanto/src/sse.zig
@@ -0,0 +1,199 @@
+const std = @import("std");
+
+/// Parsed SSE event data — the content after "data: " (prefix removed).
+/// For multi-line data events, lines are joined with newlines per the SSE spec.
+///
+/// Borrowed from the parser's internal buffer. Call `SSEParser.freeEvents()`
+/// to free the events list when done (event data itself is borrowed and
+/// does not need individual freeing).
+const Event = []const u8;
+
+/// Incremental SSE line parser.
+///
+/// The HTTP client delivers arbitrary-sized read buffers; this module
+/// reassembles them into complete `data: ...\n\n` events.
+///
+/// Event data is borrowed from the internal buffer. Call `freeEvents()` to
+/// free the events list returned by `feed`; the event data itself is borrowed
+/// from the parser's buffer and does not need individual freeing.
+pub const SSEParser = struct {
+    buf: std.ArrayList(u8) = .empty,
+    allocator: std.mem.Allocator,
+
+    pub fn init(allocator: std.mem.Allocator) SSEParser {
+        return .{
+            .allocator = allocator,
+        };
+    }
+
+    /// Feed a chunk of raw bytes. Returns a list of complete SSE events
+    /// found in the buffer. Returns an empty list if no complete events
+    /// are available yet.
+    ///
+    /// Event data is borrowed from the internal buffer. Call `freeEvents()`
+    /// on the returned list when done.
+    pub fn feed(self: *SSEParser, chunk: []const u8) ![]Event {
+        try self.buf.appendSlice(self.allocator, chunk);
+
+        var events = std.ArrayList(Event).init(self.allocator);
+        errdefer events.deinit();
+
+        var write_pos: usize = 0;
+        var scan_pos: usize = 0;
+
+        while (std.mem.indexOf(u8, self.buf.items[scan_pos..], "\n\n")) |rel_delim| {
+            const delim = scan_pos + rel_delim;
+            const event_bytes = self.buf.items[scan_pos..delim];
+
+            // Compact data lines in-place. Compacted data is always shorter
+            // than the original event bytes (we strip at least "data: " per
+            // line), so write_pos <= scan_pos and we never overwrite data
+            // we haven't yet read.
+            const data_start = write_pos;
+            var line_start: usize = 0;
+            var has_data = false;
+
+            while (line_start < event_bytes.len) {
+                const newline = std.mem.indexOfScalarPos(u8, event_bytes, line_start, '\n') orelse event_bytes.len;
+                const line = event_bytes[line_start..newline];
+
+                if (std.mem.startsWith(u8, line, "data: ")) {
+                    if (has_data) {
+                        self.buf.items[write_pos] = '\n';
+                        write_pos += 1;
+                    }
+                    const content = line["data: ".len..];
+                    std.mem.copyForwards(u8, self.buf.items[write_pos .. write_pos + content.len], content);
+                    write_pos += content.len;
+                    has_data = true;
+                }
+                // Ignore other SSE fields (event:, id:, retry:) and comments (starting with :)
+
+                line_start = newline + 1;
+            }
+
+            if (has_data) {
+                try events.append(self.buf.items[data_start..write_pos]);
+            }
+
+            scan_pos = delim + 2;
+        }
+
+        // Shift remaining (incomplete) bytes to the front, retaining
+        // the backing allocation for reuse.
+        const remaining_len = self.buf.items.len - scan_pos;
+        if (remaining_len > 0 and scan_pos > 0) {
+            std.mem.copyForwards(u8, self.buf.items[0..remaining_len], self.buf.items[scan_pos..]);
+        }
+        self.buf.shrinkRetainingCapacity(remaining_len);
+
+        return events.toOwnedSlice();
+    }
+
+    /// Free a list of events returned by `feed`.
+    /// Event data is borrowed from the parser's buffer and does not need
+    /// to be freed individually; only the events array itself is freed.
+    pub fn freeEvents(self: *SSEParser, events: []Event) void {
+        self.allocator.free(events);
+    }
+
+    pub fn deinit(self: *SSEParser) void {
+        self.buf.deinit(self.allocator);
+    }
+};
+
+test "SSEParser - single complete event" {
+    const allocator = std.testing.allocator;
+
+    var parser = SSEParser.init(allocator);
+    defer parser.deinit();
+
+    const events = try parser.feed("data: hello\n\n");
+    defer parser.freeEvents(events);
+
+    try std.testing.expectEqual(@as(usize, 1), events.len);
+    try std.testing.expectEqualStrings("hello", events[0]);
+}
+
+test "SSEParser - partial then complete" {
+    const allocator = std.testing.allocator;
+
+    var parser = SSEParser.init(allocator);
+    defer parser.deinit();
+
+    // Feed partial — no complete event yet
+    const events1 = try parser.feed("data: hel");
+    defer parser.freeEvents(events1);
+    try std.testing.expectEqual(@as(usize, 0), events1.len);
+
+    // Feed remainder — completes the event
+    const events2 = try parser.feed("lo\n\n");
+    defer parser.freeEvents(events2);
+    try std.testing.expectEqual(@as(usize, 1), events2.len);
+    try std.testing.expectEqualStrings("hello", events2[0]);
+}
+
+test "SSEParser - multiple events in single chunk" {
+    const allocator = std.testing.allocator;
+
+    var parser = SSEParser.init(allocator);
+    defer parser.deinit();
+
+    const events = try parser.feed("data: one\n\ndata: two\n\n");
+    defer parser.freeEvents(events);
+
+    try std.testing.expectEqual(@as(usize, 2), events.len);
+    try std.testing.expectEqualStrings("one", events[0]);
+    try std.testing.expectEqualStrings("two", events[1]);
+}
+
+test "SSEParser - data DONE signal" {
+    const allocator = std.testing.allocator;
+
+    var parser = SSEParser.init(allocator);
+    defer parser.deinit();
+
+    const events = try parser.feed("data: [DONE]\n\n");
+    defer parser.freeEvents(events);
+
+    try std.testing.expectEqual(@as(usize, 1), events.len);
+    try std.testing.expectEqualStrings("[DONE]", events[0]);
+}
+
+test "SSEParser - empty event (keep-alive)" {
+    const allocator = std.testing.allocator;
+
+    var parser = SSEParser.init(allocator);
+    defer parser.deinit();
+
+    // A blank line (just \n\n) is a keep-alive comment with no data
+    const events = try parser.feed("\n\n");
+    defer parser.freeEvents(events);
+    try std.testing.expectEqual(@as(usize, 0), events.len);
+}
+
+test "SSEParser - ignores non-data fields" {
+    const allocator = std.testing.allocator;
+
+    var parser = SSEParser.init(allocator);
+    defer parser.deinit();
+
+    const events = try parser.feed("event: message\ndata: payload\nid: 42\n\n");
+    defer parser.freeEvents(events);
+
+    try std.testing.expectEqual(@as(usize, 1), events.len);
+    try std.testing.expectEqualStrings("payload", events[0]);
+}
+
+test "SSEParser - multi-line data joined with newline" {
+    const allocator = std.testing.allocator;
+
+    var parser = SSEParser.init(allocator);
+    defer parser.deinit();
+
+    const events = try parser.feed("data: line1\ndata: line2\n\n");
+    defer parser.freeEvents(events);
+
+    try std.testing.expectEqual(@as(usize, 1), events.len);
+    try std.testing.expectEqualStrings("line1\nline2", events[0]);
+}